My Brake Light has stopped working on my Silverado?

First question I always ask is; do you have a trailer connector spliced in behind the bumper? 75% of the time, that's where the problem is. Please advise.

You will want to test your trailer connector to see if you have brake lights there. You're looking for an "open" in the circuit somewhere. The brake light switch has to be functioning or the cab light wouldn't be working. Please look at the wiring diagrams below. Check out the images (Below). Please let us know what happens.

You're right, the chances of both sides going bad are poor to none.
Let's start from square 1. We'll be testing at the socket for the "turn signal flasher module", under the left side of the dash. The brake lights go through this module.
The brake lights are fused seperately from a 25amp fuse(# unknown) in the underhood fuse block. This fuse should be hot all the time.
Fuse good, yes, test the orange wire at brake light switch.
Orange hot, yes, push the brake pedal and test the white wire on the BL switch.
White hot, yes? Test the white wire at the flasher module, terminal B, with brake pedal pressed.
Hot, yes?, check fuse #9 in fuse block by flasher module.
Fuse good?, yes, check the junctions and connections on the light blue wires going back to the brake light lamps.
Fuse #9 should be hot when the brake pedal is pressed.Let me know what you find.

If you aer talking about the circuit board in back of truck that doesn't have anything to do with roof lights. The brake switch wires to the fuse box and fuse then to light. I have pointed out which are which. I tmay be either a bad brake light switch or the fuse isn't making good contact in fuse box. See pic

Hi Dave and welcome to 2CarPros.

You have already done a lot. I have to ask, is there power to the switch at all times? If you take a look at the section of the wiring schematic I attached, you will see power comes from a 25 amp fuse in the under hood fuse box. It then travels to the switch via an orange wire. I need to know if there is power at the switch. Also, I need to know if the turn signals are working properly.

I've noted you indicate little knowledge. Here are a few links that will help you with checking for power, checking the fuse and power to the fuse and so on:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

and

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

If you find there is power to the switch from the orange wire, actuate the switch and check of power makes it through the switch and into the white wire.

Check out the diagrams (Below). Please let us know what happens.

Welcome back:

Often times when the signal stops flashing when you have a trailer connected, you need to replace the flasher with a HD one. Were you able to check for power to the switch?