I see that you have your question solved by opening a service request. Here is the solution for your reference:
Regarding your ModelSim licensing issue, our licensing software requires a persistent connection to the license server. It's somewhat tolerant of network glitches. However, actions like undocking or closing the application during a network outage can leave licenses indefinitely checked out on the server. We recommend against undocking, sleeping or hibernating while the application is running. ModelSim should be closed first so the license can be properly checked in.