Might be a silly question but, when you gave the handbrake switch a tap was the handbrake off?
Maybe the shuttle valve has shifted in the proportioning valve. If the dash light goes off with the switch disconnected below the reservoir then the shuttle valve has shifted. Mrblaine on jeepforum usually suggests stomping down on the pedal several times to get the valve to reset.
It's possible you may need to bleed the back brakes, which would lower the pressure on the rear circuit to equalise the pressure on front/rear circuits and reset the valve.