Zoo "Recover" grayed out after updating to 9/27/2018 version

A problem on our Zoo server – running out of system resources – led to a large number of unreturned licenses filling up the license pool and these didn’t clear, on Refresh, when system resources were restored. Using Edit–>Recover these were able to be reclaimed but the server still did not automatically reclaim others where there was no longer a copy in use. This led to updating the Zoo version (two updates were needed) to the current 9/27/2018 release. While this process did clear up the majority of unreturned licenses, the “Recover” option is now unavailable – it’s still listed on the Edit menu but grayed out and not able to be selected for any license in use. The license server service has been restarted several times (although the license server machine, which also serves other licenses, hasn’t). We haven’t added any new license plug-ins since the time the Recover option was available. What could be going on?

Recover is intended for manually returning licenses that have been checked out and for some reason, the license can not be checked back in normally.

If the selected license in the Zoo console is not “checked out”, then recover isn’t a valid operation so the command is grayed out.