You get VM Unknown when the ESXi host can’t open the vmx file that tells the host about the VM.
To fix this:
Remove the VM from the ESXi hosts inventory (don’t delete the files, just remove it)
From another ESXi host, open the datastore and navigate to the VM’s config files
Right click the vmx file and click Add to inventory
The VM should now be up and running and you are free to troubleshoot the ESXi host as to why it can’t connect to the storage correctly. If the problem lies with the storage, once you’ve fixed the storage / network issue, don’t forget to restart the ESXi management agents.