Will the blocked devices be accessible when the AccessPatrol server is not running?

The AccessPatrol Client retains data on the client-side. If the server is unavailable, the permissions will still be applying to the client computers.

If you want to turn this feature off, right-click on the group > Client Settings. Uncheck the option Apply block settings when the server is unavailable. If this option is unchecked, when the server becomes unavailable, the client computers will not be blocked.