no power for brake lights at the brake light switch

Did you check the fuse? Not only check the fuse, use a test lite on fuse circuit, hot all the time. Note the diagram.

Checked fuse box , fuse was good BUT loose. Looks like fuse sockets had gotten warm and would no longer hold fuse securely resulting in intermittent and eventually no operation,repair sockets or replace fuse box, lights and cruise control now work normal

I own a 2015 Ford F350 Superduty , and my trailer switch was wired wrong so when I inserted the switch into the 7 way connection into my Truck the lights flickered and went off also as soon as I turned the truck off it will not start again , luckily I had a remote start and the truck started , The trailer burnt the a fuse under the passenger's side and a square fuse under the hood # 90 a 25 amp fuse , It was hard to tell because it's very hard to test these ,

Fuse block was bad , wouldn’t hold the fuse securely anymore.Changed out fuse block

Good job.