When HA is enabled, some operations that would compromise the plan for restarting virtual machines may be disabled, such as removing a server from a pool. To perform these operations, you can temporarily disable HA.
To disable HA:
Select the pool in the Resources pane, click on the HA tab, and then click Disable HA.
to confirm. The VM startup settings specified for each VM in the pool are stored and
will be remembered if you turn HA back on again later.