When you opened the panel, the panels internal tamper switch was triggered. If it has not cleared, it is likely that the switch is askew, or not being pushed down fully by the back plate.
Check the back plate, is it firmly seated against the panel using the set screw, or are there gaps/ is the back plate crooked?
Internally, are there any power or antenna wires getting in the way of the backplate?
If you press down on the tamper for a bit, then release, does the panel tamper or is the switch kind of stuck a bit?
Once you have received the alarm permit number, be sure to relay that to us (you can send it via private message) so we can associate the number with your monitoring account.