Stuck Rhino 6 windows Zoo license server

Rhino applications are no unable to communicate with the Zoo License server. Zoo shows one checkout of a user from a week ago but the user states it has not used the application the last couple of days and is now not able to checkout licenses. Other users have reported the same issue with Rhino connecting to the Zoo license server.
The license server service has been restarted and the Windows OS has been restarted to no avail, it still shows the old license checkout. How can we reset the Zoo license server?

There may be some answers here:

https://wiki.mcneel.com/zoo/home

Thank you for taking the time to respond. It turns out the issue was not with the license server itself but wit users reporting issues that we could not confirm with the license admin tool, leading us to believe that the license daemon was stuck.