Okay… This was a first for me. I was in VCSA and went to vMotion a VM, a totally normal task. However, upon clicking on the VM and trying to run the vMotion, it option was greyed out. WHAT THE HECK!?!
Well, thankfully it ended up being a simple fix. Apparently, this can happen if the VCSA database does not get properly updated after a backup job. Here’s how to re-enable it.

Manually remove entries from the vCenter Mob:

1. Identify the VM’s MOB ID
   1. Open a web browser and go to the vCenter vSphere Client (HTML5)
   2. In the left hand side inventory, select the affected VM’s object
   3. With the VM selected and highlighted, in the URL bar, review the string and look for “VirtualMachine:vm-xx“

Example: https://<VCSA-FQDN>/ui/#?extensionId=vsphere.core.vm.summary&objectId=urn:vmomi:VirtualMachine:vm-69:7071ab73-c123-4d56-ef78-1234gh56i7jk&navigator=vsphere.core.viTree.hostsAndClustersView

In this example VM’s MOB ID is vm-69.

2. ​​​​​​Access the Virtual Machine Operations by opening a web browser to: 

https://<VCSA-FQDN>/mob/?moid=AuthorizationManager&method=enableMethods

3. Login with administrator@yourssodomain.local or an SSO admin user (administrator@vsphere.local)
   
4. The below page will appear:

5. In the first parameter entity value box, replace MOID with the VM’s MOB ID

<!– array start –>
<entity type=”ManagedEntity” xsi:type=”ManagedObjectReference”>vm-69</entity>
<!– array end –>

6. In the second parameter entity value box, enter this command:

<method>RelocateVM_Task</method>

7. Click on “Invoke Method” in the lower right corner.

8. Refresh the vCenter Server web client and the migration option for the VM should now be available. If the issue persists, try restarting all of the vCenter Server services.

Here is VMware’s KB about it.