I recently bought a TT and when I connected to my truck and got down the road I went to squeeze the trailer brake and it did it once then it said the trailer was disconnected and I couldn’t use them again but my lights still worked ...any info would help

 

Start by cleaning the trailer plug and truck socket

 

New TT? Most common issue of sliding the brake lever and getting the no trailer warning is an intermittent trailer brake wiring issue on older trailers.

Clean out the plug really well, road debris is conductive. Been there, done that.

Also clean and grease the plugs behind the bumper. Water is your enemy there.

There's also a ground connection there that can cause issues.