vSphere Web Client - Unmount Datastore Grayed out.

It was time to decommission one of our iSCSI datastores.  I ensured the following:

• All VMs, snapshots and templates have been migrated off.
• Datastore is not used for HA heartbeat
• Not part of a datastore cluster.
• Not configured as a coredump partition
• Storage I/O Control disabled 

**Go through the complete unmounting a LUN checklist prior to unmounting a LUN: 

https://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2004605 

When I tried to unmount the datastore, using the vSphere Web Client, the option was grayed out...

Workaround: 
After going through the detailed checklist in VMware KB 2004605  I went OLD SCHOOL and used the VMware vSphere Client to log directly into the host using the Datastore.  Through the vSphere Client, I was able to successfully unmount the datastore.

FYI - You can still point your vSphere Client directly to an ESXi 6.5 host.

Jan 23rd 2018 Update:

It happened again, this time I used the web client pointed directly at the ESXi host to perform the unmount function: