You keep getting below error whenever you try to put your hypervisor/host to Maintenance Mode.
"Failed to change status of host Hypervisor01 due to a failure to stop the spm"
-Force SPM to restart on the other hypervisor/host.
-SSH to specific hypervisor/host and restart vdsmd services.
systemctl restart vdsmd
Since the Red Hat Enterprise Virtualization or oVirt Manager ensures that the SPM is always available, the Manager will moves the SPM role to a different host if the SPM host encounters problems accessing the storage.
In our case, SPM is running in Hypervisor01, when you restart vdsmd service, manager will force SPM role to start on the other Hypervisor (Hypervisor02, 03 or whatever you name it). After SPM have moved to another Hypervisor, you can put Hypervisor01 to maintenance mode.