There is most likely an issue with the MDC and the daemon may need to be restarted to allow the SAN clients to mount the filesystem. Since we don't debug logs on our forums, the only verification would be for us to examine the logs via a documented support case via our Support Portal.
1. Make sure to unmount the FC SAN client that still have the filesystem mounted.
2. Stop the filesystem via the GUI as this will facilitate the process of unmounting the NASGW shares.
3. Reboot the A-Class via GUI or CLI.
4. Once the A-Class is back online, start the filesystem via GUI or CLI.
5. After the filesystem has successfully started, mount the filesystem on your macOS SAN clients.
5A. You should not receive the same error.
6. Make sure to re-mount all the share(s) on your NASGW cluster.
If you are still experiencing issues, please document your case via https://support.promise.com and a tech support agent will be assigned to your case.