Try restarting the services in Windows button, Run, services.msc all that start with QlikView. Make sure that in the QlikView Enterprise Management Console, System, Licenses, QlikView Server (click on yours) and on the right side, Client Access Licenses (CALs), Assigned CALs, there are actually 24 hours or longer difference between the columns Last Used (UTC) and Quarantined Until (UTC).
Note that times are UTC, meaning that for example in my case, I have to add 2 hours to the time shown in the Console.
If either the difference is 24 hours or longer, or the Last Used is older than 24 hours ago, you should be able to remove the assignment directly.
Hope that helps.