Issue
Backups for a protected endpoint fail with the error message, "Error 131: Connect lost during backup operation."
Environment
NinjaOne Backup
Cause
NinjaOne could not establish a connection to the protected endpoint, or the connection was lost during a backup operation. This issue can occur at the start of the backup job during preparation, or during a backup job with different causes and solutions.
When the issue occurs at the start of a backup job, it indicates that the pre-job process began but could not contact the backup agent, or the backup agent failed to communicate with the necessary backup resources during the job. The scenario suggests a communication failure between the pre-job environment, the backup agent, and the backup resources.
When the issue occurs during a backup job, bad data blocks may be the cause. Backup jobs can get stuck trying to read a block and terminate in a failure state. Check your backup logs to confirm the root cause. "GET INFO FROM SUPPORT" verbiage appearing in your Windows event logs can also indicate this scenario as the likely cause of the failure. might also be present in Windows event logs.
Resolution
Verify general network connectivity by pinging NinjaOne resources from the protected endpoint to ensure they are reachable. Check that your firewall and antivirus settings are not blocking access to file paths scheduled for backup. Review endpoint event logs for disk errors and run disk integrity scans to identify and remediate any problems.
After completing these steps, attempt the backup job again to confirm successful issue resolution.
Additional Resources
For additional troubleshooting guidance, refer to NinjaOne Backup: Troubleshooting Error Codes.