Can't return borrowed licenses

Today, none of the user on our network could return their borrowed licenses. We al get the error meassage "Could not return the Solidworks [Standard/Professional] license. No such feature exists.". All licenses are shown on the server as free and available and the borrowed licenses are not shown as unavailable in the SolidNetWork License Manager. The machines with borrowed licenses can all run SolidWorks.

I have tried stopping and restarting the license server as well as rereading the licenses. Any ideas on how to proceed?

SolidworksAdministration