Microsoft 365 Troubleshooting: Common Issues and Solutions
Something not working in Microsoft 365? You're in the right place. This guide covers the most common problems and how to fix them—no IT degree required.
Find your issue below and follow the steps.
Activation Problems
'Unlicensed Product' or 'Product Activation Required'
- 1.Open any Office app > File > Account
- 2.Click 'Sign Out' under User Information
- 3.Close all Office apps completely
- 4.Reopen an Office app and sign in with the correct Microsoft account
- 5.Make sure you're using the email linked to your subscription
Still broken? Check your subscription status at account.microsoft.com/services. If it shows active, run the Support and Recovery Assistant from aka.ms/SaRA.
'This product key has already been used'
- 1.The key is already linked to a Microsoft account
- 2.Try signing in with other email addresses you own
- 3.Check office.com/myaccount with each email
- 4.If you bought from a third party, the key may be fraudulent—contact the seller
Still broken? Contact Microsoft Support with proof of purchase. They can sometimes help recover legitimate keys.
'We can't verify your product key'
- 1.Double-check every character in the key (0 vs O, 1 vs I)
- 2.Make sure you're entering it at office.com/setup
- 3.Try a different browser
- 4.Clear browser cache and cookies
Still broken? The key may be invalid. If purchased from unauthorized seller, you may need to dispute the charge.
Installation Issues
Installation stuck or frozen
- 1.Wait at least 30 minutes—large downloads can appear stuck
- 2.Check your internet connection
- 3.Restart your computer and try again
- 4.Temporarily disable antivirus software
- 5.Download the offline installer from office.com/setup instead
Still broken? Use the Office uninstall tool (aka.ms/SaRA), then reinstall fresh.
'Something went wrong' during installation
- 1.Uninstall any old Office versions first (Settings > Apps)
- 2.Run the install as Administrator (right-click > Run as administrator)
- 3.Make sure Windows is fully updated
- 4.Check you have at least 4GB free disk space
Still broken? Download the Support and Recovery Assistant from aka.ms/SaRA—it fixes most installation issues automatically.
Office apps missing after installation
- 1.Search for 'Word' or 'Excel' in the Start menu
- 2.Check if apps are in C:\Program Files\Microsoft Office
- 3.Try signing out of office.com and signing back in
- 4.Click 'Install Office' again—it may have partially failed
Still broken? Fully uninstall using aka.ms/SaRA tool, restart, then reinstall.
OneDrive Sync Problems
Files not syncing
- 1.Check the OneDrive icon in system tray—is there a red X or pause icon?
- 2.Click the icon > More > Resume syncing
- 3.Make sure you're connected to the internet
- 4.Check if OneDrive storage is full (1TB limit)
- 5.Right-click OneDrive icon > Settings > Account > Unlink this PC, then set up again
Still broken? Reset OneDrive: Press Win+R, type '%localappdata%\Microsoft\OneDrive\onedrive.exe /reset' and hit Enter.
Sync conflicts (duplicate files)
- 1.OneDrive creates copies when the same file was edited in two places
- 2.Open both versions and manually merge changes
- 3.Delete the version you don't need
- 4.To prevent: always let sync complete before editing on another device
Still broken? Check Version History: right-click file in OneDrive > Version history to restore older versions.
'File is locked for editing'
- 1.Someone else has the file open—wait for them to close it
- 2.Check if YOU have it open on another device
- 3.Close all Office apps, wait 10 minutes, try again
- 4.Open the file in read-only mode and save as a new copy
Still broken? As a last resort, make a copy of the file with a new name.
Apps Crashing or Freezing
Word/Excel/PowerPoint crashes on open
- 1.Open the app in Safe Mode: Hold Ctrl while clicking the app icon
- 2.If it works in Safe Mode, a plugin is the problem
- 3.Go to File > Options > Add-ins > Manage: COM Add-ins > Go
- 4.Disable all add-ins, then enable one at a time to find the culprit
Still broken? Run Quick Repair: Settings > Apps > Microsoft 365 > Modify > Quick Repair.
App freezes while working
- 1.Wait 2-3 minutes—it may be processing a large file
- 2.Press Ctrl+Alt+Delete > Task Manager > End the frozen app
- 3.Check if AutoRecover saved your work (File > Info > Manage Document)
- 4.Disable hardware graphics acceleration: File > Options > Advanced > uncheck 'Disable hardware graphics acceleration'
Still broken? Update your graphics drivers. Outdated drivers cause many Office freezes.
Crashes when opening specific file
- 1.The file may be corrupted
- 2.Try opening it on another device or in the web app (office.com)
- 3.Open Word/Excel first, then File > Open > Browse > select file > click arrow next to Open > Open and Repair
Still broken? If the file won't repair, try recovering content: open a new document, Insert > Object > Text from File > select the corrupted file.
Slow Performance
Office apps slow to start
- 1.Disable unnecessary add-ins (File > Options > Add-ins)
- 2.Clear the Office cache: delete contents of %localappdata%\Microsoft\Office\16.0\OfficeFileCache
- 3.Make sure you have at least 10% free disk space
- 4.Update to the latest Office version (File > Account > Update Options > Update Now)
Still broken? Run Online Repair: Settings > Apps > Microsoft 365 > Modify > Online Repair (takes longer but more thorough).
Excel slow with large files
- 1.Reduce formulas: convert some to values (Copy > Paste Special > Values)
- 2.Delete unused rows/columns (Ctrl+End shows actual used range)
- 3.Remove conditional formatting from large ranges
- 4.Split data across multiple sheets or files
- 5.Disable automatic calculation: Formulas > Calculation Options > Manual
Still broken? 64-bit Office handles large files better. Reinstall with 64-bit if you're on 32-bit.
Outlook running slow
- 1.Reduce mailbox size: delete old emails, empty Deleted Items and Junk
- 2.Compact your data file: File > Account Settings > Account Settings > Data Files > select file > Settings > Compact Now
- 3.Disable unnecessary add-ins
- 4.Turn off automatic download of images in emails
Still broken? Create a new Outlook profile: Control Panel > Mail > Show Profiles > Add. Then set as default.
Login & Account Issues
Can't sign in to Office apps
- 1.Check your internet connection
- 2.Try signing in at office.com first—if that works, the desktop app has an issue
- 3.Clear Office credentials: Control Panel > Credential Manager > Windows Credentials > remove entries with 'Office' or 'Microsoft'
- 4.Restart your computer and try again
Still broken? Sign out from account.microsoft.com/devices on all devices, then sign back in on your main device.
Wrong account showing in Office
- 1.File > Account > Sign Out
- 2.Close all Office apps
- 3.Open any Office app and sign in with the correct account
- 4.If multiple accounts needed: File > Account > Add Account
Still broken? Clear all Office accounts from Windows: Settings > Accounts > Email & accounts > remove Office-related accounts, then re-add.
'Your account doesn't allow editing on a Mac'
- 1.This usually means you're signed in with a personal account that doesn't have a license
- 2.Sign out and sign in with your work/school account
- 3.Or sign in with the Microsoft account that has the 365 subscription
Still broken? Delete Office license files: Finder > Go > Go to Folder > ~/Library/Group Containers/ > delete folders starting with 'UBF8T346G9' > restart Office.
Outlook Problems
Outlook can't connect to email server
- 1.Check your internet connection
- 2.Try Outlook on the web (outlook.com)—if that works, it's a desktop issue
- 3.Restart Outlook in Offline mode: Send/Receive > Work Offline (click to toggle)
- 4.Remove and re-add your email account: File > Account Settings > select account > Remove, then Add
Still broken? Create a new Outlook profile with fresh settings.
Emails stuck in Outbox
- 1.Check if you're in Offline mode (Send/Receive > Work Offline should be unchecked)
- 2.Open the stuck email, make a small change, close and try sending again
- 3.Check if attachment is too large (most servers limit to 25MB)
- 4.Move email from Outbox to Drafts, then try sending again
Still broken? Delete the stuck email from Outbox and recreate it.
Search not finding emails
- 1.Outlook may still be indexing: File > Options > Search > Indexing Options > check status
- 2.Rebuild search index: Indexing Options > Advanced > Rebuild
- 3.Make sure the folder you're searching isn't excluded
- 4.Try searching with fewer/different terms
Still broken? Repair the Outlook data file: Close Outlook, run 'SCANPST.EXE' from C:\Program Files\Microsoft Office\root\Office16.
Nuclear Options (When Nothing Else Works)
Tried everything? Here are the big reset options:
Quick Repair
Fixes most issues without losing data. Takes 5-10 minutes.
Settings > Apps > Microsoft 365 > Modify > Quick Repair
Online Repair
Complete repair using internet. Takes 30-60 minutes. Fixes more issues.
Settings > Apps > Microsoft 365 > Modify > Online Repair
Complete Uninstall + Reinstall
Removes everything and starts fresh. Last resort.
1) Download Support and Recovery Assistant from aka.ms/SaRA 2) Run it and select 'Uninstall Office' 3) Restart computer 4) Reinstall from office.com
Online Repair and Reinstall will require you to sign back in and may reset some preferences. Your documents and files are safe—they won't be deleted.
Still Need Help?
- •Microsoft Support: support.microsoft.com (live chat available)
- •Microsoft Community Forums: answers.microsoft.com
- •Support and Recovery Assistant: aka.ms/SaRA (automated fixes)
- •For business accounts: Contact your IT administrator first