UA planes offer between 21-24 PE seats. You’re talking about over 20% of the cabin, and PE has been extremely popular since it was introduced. (UA flights regularly oversell PE and count on people upgrading to J).

If you can split up into two groups, you might be able to find PE space. If not, it was pretty much an impossibility. (Incidentally, that’s also why you couldn’t be re-accommodated for two days; it’s hard even to find 5 Y seats consistently). I would never recommend anyone traveling with more than 2 people fly PE on UA unless they’d be OK flying in Y if things went sideways.

This obviously doesn’t help much now, unfortunately, but hopefully it’ll be good information for someone else reading this thread in the future.

Good luck!