License Server holding licenses

I had to shut down my slaves today (just for a power changeover) and when I brought them back up the license server is holding onto the old licences and so now most of my slaves arent licensed. Is there a way to force the license server to release licenses and then force slave to relicense?

You could just restart the license service on your license server?
The Slaves will automatically check at regular intervals and re-gain a license. Give it 10 mins or so.

looks like they figured it out. They were running for over an hour and hadnt relicensed. Overnight they seem to have done it. Maybe they just dont like it people watching them…