SCOM reports a Warning: "Failed Accessing Windows Event Log...". and in the State Change Events description you can find:
"The Windows Event Log Provider was unable to open the nworksEventLog event log on computer 'node_xxx' for reading. The provider will retry opening the log every 30 seconds. Most recent error details: The specified channel could not be found. Check channel configuration. One or more workflows were affected by this. Workflow name: many Instance name: many Instance ID: many Management group: ClusterName "
To fix this issue you can try rebuilding topology from nworks UI -> "Enterprise Manager" tab -> select "Enterprise Manager" node in the left pane -> Rebuild Full Topology.
If this does not help, contact Veeam Support for further troubleshooting.