We identified that device.dattobackup.com experienced issues after renewing our certificate. For a subset of customers with specific outbound traffic on port 443 restricted, this change required additional firewall adjustments, which increased operational effort.
To reduce this burden and restore a more consistent experience, we updated the SSL certificate for device.dattobackup.com at approximately 4:00 PM ET on Friday, January 23, 2026.
Since the update, we have observed a significant reduction in certificate renewal–related errors. Our team is actively monitoring the environment to ensure ongoing stability.
Please be advised that if certificate‑related errors persist, a restart of the Agent services is required to restore standard operational functionality.
We appreciate your patience during this process. Please let us know if you are still experiencing any issues or if you have questions—we’re here to help.
Posted Jan 26, 2026 - 11:54 EST
Monitoring
We have pushed an update to alleviate the error "Critical backup failure during data transfer (Certificate error communicating with Agent)".
In order for this update to fully take effect, the Datto Backup Agent Service needs to be restarted on the protected server.
If the backup continues to fail, or the repair agent communications fails, please contact Technical Support for further guidance.
Posted Jan 23, 2026 - 19:26 EST
Identified
We have identified an increased rate of backup failures due to error "Critical backup failure during data transfer (Certificate error communicating with Agent)" for Datto BCDR products.
Our R&D team has been alerted to this and is actively investigating the issue, however, If you have agents experiencing this error, please ensure that the agents have outbound access to the following on port 443:
device.dattobackup.com
cf-dl.datto.com
agent-update.datto.com
mothership.dtc.datto.com
tmp.datto.net
ocsp.digicert.com
e8.i.lencr.org
valid-isrgrootx1.letsencrypt.org
Please take a moment to review the network requirements outlined below, as any deviations from these configurations may contribute to the behavior you are experiencing:
Verifying that these configurations are properly implemented will help eliminate known environmental variables as potential contributors.
Additionally, please be aware that certain firewall traffic inspection features may also contribute to these conditions.
More information will be shared as it becomes available.
Posted Jan 20, 2026 - 13:02 EST
Investigating
We have identified an increased rate of backup failures due to error "Critical backup failure during data transfer (Certificate error communicating with Agent)".
Our R&D team has been alerted to this and is actively investigating the issue.