Globally unique resources that provide access to data management services and serve as the parent namespace for the services.
I think this needs Azure Storage support case. GPv1-to-GPv2 preserves data, so the upgrade alone doesn't explain the missing files. Check the share in Azure portal > File shares > Browse and compare with SMB. A Browse failure can also be a permissions issue.
If the share is deleted, check Show deleted shares. If files are missing, check pre-loss snapshots and Azure Backup recovery points. An existing vaulted recovery point can restore the full share elsewhere, even if the source snapshot is gone. Avoid overwrites. Send Support the resource ID, share name, UTC timestamps and errors.