It looks like you are using a 2GIG GC3. Your GC3 has launch firmware on it (3.0.0) and I would recommend updating to at least 3.1.3 for general stability benefits.
We’ve heard a few reports from GC3 and GC2 users where a panel screen went black. This is a rare error more common on older firmware, generally a reboot helped in most cases.
You can send a remote reboot command from the System Manager here.
Did you do anything to troubleshoot the screen or did it just come back on its own?