Funny thing about this: yesterday I used the tractor to move something heavy and long, too long to use the forks and get it through gates and down a road (a very wide roll of netting we use for fruit trees vs birds). One end I put on the tiller that's on the 3ph, the other end was on a wagon, and the pipe going through the roll that supports it usually I shoved farther in so it wouldn't stick out so far.
A while later after getting the roll set up in its new location, I found the 3ph wasn't operating. All other hydraulics were fine, I'm like "ok so NOW there's suddenly an electrical thing about this?" but no on closer inspection when I knocked the pipe it hit the backhoe loop connector that keeps the two hoses together just right and while superficially the loop looked complete because of how the hose is being held there, the two ends were no longer connected...
and I thought of this post and how "without the backhoe you have to connect the loop... for the 3ph"
Bingo!