Long version of what is going on for a bunch of us is here:
https://www.f150gen14.com/forum/threads/trailer-brake-not-working.3039/
Short version is that there is an intermittent issue with the TBC not working either at the start of the trip of randomly part way through. It's not the trailer as many of us have had them checked out thoroughly, and the issues are common.
Just wanted to get as much visibility to this problem and a potential solutions, other than Ford getting off their butts and figuring it out!
It's really frustrating as I love everything about this truck otherwise!
2021 F-150 HDPP EcoBoost
2016 Coleman 262BH
Reese Dual Cam - 1200lb