JLG 2630 Sort-of-dead

My scissor lift worked great when we last parked it in the shop about a month ago. I keep it plugged in and on a timer so that it gets charged a few hours a week when we are not using it. When plugged in, the battery charge indicatior shows green, which is supposed to mean "full". The batteries are about 6 months old. We replaced all of them earlier this year. I've checked the batteries and all are good, up to voltage and the connections look good. There is a key switch to select ground control or platform control. When we select either mode, the multi-function display wakes up, flashes a code of E5002 for a moment, then the code goes away, the battery display shows full, and it looks like all is well. Except nothing works. There is a switch on the ground control to raise and lower the lift. It does nothing. If I put it in Platform Mode, none of the switches on the platform work. Zip. Not even the horn. I tried to hit the electric brake release switch so that I could roll the unit into a more convenient place to work on it, and that button has no effect either. Usually, hitting that switch results in a small solonoid noise from the wheels. Now it does nothing. I have the JLG diagnostic analyzer. I plug it in, and it says all is well. No errors. It even confirms when every switch is activated. If I push platform up, it tells me "platform up switch closed" . It does this for every switch. It says that everything is fine. It looks at all of the tilt/stress sensors and all of those say that they are fine also. We clearly have full battery power. The control wiring seems fine. There is a red LED on the ground station printed circuit board that will flash an error code when there is an error, but it is just steady-on now. Im not sure if that is normal or not and the manual doesn't seem to say one way or another. I'm running out of ideas. Can anyone suggest something else to look for?