Hey guys, I thought I'd just post this here in case someone else comes by with the same problem. For the first time, I hooked up the disco to a trailer and connected the lights. As soon as I did that, the diff warning light would come on when I touched the brake and the car refused to shift out of park. I was able to remove the cover and depress the solenoid pin manually, but after disconnecting the trailer the problem persisted. All the brake lights were functional. I checked fuse 21 [(15A) Ignition switch key hold solenoid, transmission shift warning buzzer] and it was fine and then started swearing mightily. After pouring over solutions on the forum, someone mentioned checking fuse 25 [(15A) Reversing lamp/s, stop lamps] as well. Lo and behold, it was popped! I replaced 25 and everything went back to proper function.

If this happens to you, make sure to check both 21 and 25! Hope this helps someone in the future!

 

Thanks for the follow up! As someone who has utilized MANY past postings, it's super frustrating when the issue isn't followed up with.