The knowledge base has no specific answer yet for a general “stopped syncing” case beyond these checks:
1. Check the sync status and logs.
2. Make sure the folder is selected for sync.
3. Check file filters.
4. Check if the file is restricted.
5. Check if antivirus software or firewalls are enabled.
6. Check the maximum number of files allowed.
7. Check if files are indexed correctly in Synology Drive.
8. Check if files sync after being moved out and back in.
9. Contact Technical Support.
Also, if you see a specific Synology Drive Client task error, the knowledge base lists these common cases:
- Untrusted SSL certificate
- SSL certificate has been changed
- Authentication error
- Connected to a different server. Please create a new task
- Your Synology Drive Client version is not up-to-date. Please update your Synology Drive Client
- Incompatible server version. Please make sure the versions of Synology Drive Client and Synology Drive Server are consistent
- Access from your current IP address is denied
- Your user account does not have access privileges to Synology Drive Server
- Less than 2 GB available on Synology Drive Server
- Your local disk space is full
- Server shared folder is unmounted
- Initialization failed
If you want, I can help you map the exact error message to the relevant fix from the knowledge base.
Sources used: [6], [11], [12]