After Migration to new vCenter vSAN cluster is reporting as Witness host not found.
VMware vSAN (All Versions)
The stretched cluster no longer contains a valid witness.
Verify object health is in a reduced available state with no inaccessible objects, and proceed with disabling the stretched cluster configuration and then reconfigure using the correct witness host.
This will correct the error and allow the cluster to sync correctly.
If you have any additional questions, or concerns regarding this issue please open a case with VMware Support for further investigation.