You try to attach a file in a Teams chat, but the upload fails or the file never appears. This often happens when OneDrive sync is enabled on your computer, causing conflicts or permission errors. The problem usually stems from OneDrive sync blocking the file, a corrupted local cache, or a Teams app glitch. This article explains the root cause and gives you clear steps to fix the upload issue.
Key Takeaways: Fix Teams Chat File Upload Failing with OneDrive Sync
- Pause OneDrive sync: Temporarily stops sync conflicts that block file uploads in Teams chat.
- Clear Teams cache: Removes corrupted local files that prevent attachments from uploading.
- Use Teams on the web: Bypasses desktop app issues when OneDrive sync is active.
Why OneDrive Sync Blocks File Uploads in Teams Chat
When you enable OneDrive sync on your Windows computer, it continuously monitors your local files and uploads changes to the cloud. Teams chat uploads rely on the same OneDrive infrastructure. If a file is locked by sync, has a pending sync state, or is stored in a folder that OneDrive does not fully recognize, Teams cannot attach it. The upload either fails silently or shows an error like “Upload failed” or “File not found.”
Another common cause is a corrupted Teams cache. Teams stores temporary data locally, including upload metadata. When this cache becomes outdated or damaged, it can interfere with the upload process. This is especially noticeable after a Teams update or a system restart.
How OneDrive and Teams Interact
Teams uses OneDrive for Business to store files that you share in chats. When you attach a file, Teams uploads a copy to your OneDrive and then shares a link. If OneDrive sync is running, it may hold the file in a read-only state or mark it as “sync pending.” This prevents Teams from reading the file correctly. The issue is more likely with files that are large, recently modified, or stored in a folder that is not fully synced to the cloud.
Steps to Fix File Upload Issues in Teams Chat
Follow these steps in order. Test the upload after each step to see if the problem is resolved.
- Pause OneDrive sync
Right-click the OneDrive cloud icon in the system tray. Select “Pause syncing” and choose “2 hours” or “8 hours.” This stops sync conflicts temporarily. Try uploading the file again in Teams. - Clear Teams cache
Close Teams completely. Press Ctrl+Shift+Esc to open Task Manager. End all processes named “Microsoft Teams.” Press Win+R, type %appdata%\Microsoft\Teams, and press Enter. Delete all files and folders inside this directory. Restart Teams and try uploading again. - Check file permissions
Right-click the file you want to upload. Select “Properties.” Go to the “Security” tab. Ensure your user account has “Full control” or at least “Read & write.” If not, click “Edit” and grant yourself permissions. Then try uploading. - Move the file to a local folder
If the file is inside a OneDrive-synced folder, copy it to a folder that is not synced, like C:\Temp. Then attach the copy in Teams. This avoids sync locks entirely. - Use Teams on the web
Open your browser, go to teams.microsoft.com, and sign in. Start a chat and try uploading the same file. If it works, the issue is isolated to the desktop app. You can continue using the web version while you troubleshoot. - Check Teams service health
Go to the Teams admin center at admin.teams.microsoft.com. Under “Health,” select “Service health.” Look for any incidents related to OneDrive or file sharing. If there is an outage, wait until it is resolved.
If Teams Still Has Issues After the Main Fix
Teams Shows “Upload Failed” for a Specific File
If only one file fails, the file may be corrupted or too large. Teams has a file size limit of 1 GB per attachment. Compress the file into a ZIP archive and try again. If the file is an Office document, open it and save it as a new file to reset its metadata.
OneDrive Sync Keeps Restarting Immediately
If pausing sync does not help, OneDrive may have a corrupted sync state. Right-click the OneDrive icon and select “Settings.” Go to the “Account” tab and click “Stop sync.” Then restart OneDrive and let it re-sync. This resets the sync engine without deleting any files.
Teams Chat Upload Works Only After Restarting the Computer
This suggests a memory or resource leak in the Teams app. Update Teams to the latest version. Go to the three-dot menu in Teams, select “Check for updates,” and restart the app. If the problem persists, reinstall Teams: uninstall it from Settings > Apps, then download the latest installer from the Microsoft website.
Teams Desktop with OneDrive Sync vs Teams on the Web
| Item | Teams Desktop with OneDrive Sync | Teams on the Web |
|---|---|---|
| File upload method | Uses local file system and OneDrive sync engine | Uploads directly from browser without sync interference |
| Sync conflict risk | High when OneDrive is actively syncing | Low because no local sync process runs |
| Cache corruption | Possible and requires clearing cache | Rare; browser cache is separate |
| File size limit | 1 GB per file | 1 GB per file |
| Best for | Users who need offline access and deep integration | Quick fixes and troubleshooting |
You can now fix the upload failure by pausing OneDrive sync, clearing the Teams cache, or switching to the web version. Start with pausing sync and testing the upload. If the issue persists, clear the cache as described. For a permanent solution, consider using Teams on the web for frequent file sharing. You can also set OneDrive to pause sync during your work hours using the “Pause syncing” option in its settings.