Morning!

400ft may just be too far, internet seems to point to 328 being the acceptable maximum.

I would first try re-crimping the ends since that's the easiest fix. Cat6 (at least to me) seems to be a little trickier with looking like the pins are connected but they aren't.

When you say didn't cycle like normal. Do you mean some lights didn't come on but some did, or that one end of the tested essentially did nothing?

Wonder if something like this would work: https://www.amazon.com/Extender-Gigabit-IEEE802-3af-Security-Splitter/dp/B07FMNHYP8/ref=sr_1_5?keywords=PoE+Extender&qid=1677520057&sr=8-5