Whilst migrating some service roles from Windows server 2008 R2 to Server 2016 I noticed that the Veeam backups of the new servers were failing with the error Failed to check whether snapshot is in progress (network mode). RPC function failed. Function name [IsSnapshotInProgress] Target Machine [MachineName] RPC error. The RPC server is unavailable. Code 1722.
It seemed likely this is a firewall issue, and it turns out it was.
It was pretty simple to resolve once I knew which firewall to enable. Enable the rule Remote Service Management [RPC-EPMAP]. This will allow the job to continue. This rule is disabled by default in server 2016.