Open up the backbox and check ALL fuses. Take them out one at a time and verify their value (finely etched into the end cap) matches what is called for in the manual. Continuity beep-test them with a meter. All correct and good?

Refer to manual and locate and verify ALL status LEDs on Power Driver Board and WPC controller. Are any unlit?

Inspect around the three batteries on the WPC controller board for fuzzy white or green stuff.

working off memory, but also check that the settings have not been set to disable either Thing or the Bookcase. (not sure if thats available but I thought it was)

I have seen this issue on another TAF that I played on route....dirty game, DMD was shot and both the bookcase and Thing were not working.

Gotta love pins.....You move em, and they decide to not work anymore

Yes, moving changes things. Especially check the short ribbon cable between WPC and Driver.

Yeah, I think both those assemblies can be listed as Broken in tests which defeats their operation. If the game detects switch failures with them long enough it will automatically disable them.

I think the extent of the corrosion will determine if it's repairable within reason. Might try contacting chrishibler and send him some pics of the damage. He can tell you if its repairable or not. He did both my mpu and power boards for my TAF.