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.