Had a similar issue with my 2025 Chevy 2500 HD. Did everything (forget phone, forget truck etc) Ended up resetting (rebooting) the infotainment system, using the "phone hang-up" button on the right side of the steering wheel, holding it down until the infotainment system reboots. All good now.
These trucks use "hacked up" Pulse Width Modulated DC going back to the trailer connection for the trailer lights. The camera uses the same PWM DC voltage to power your camera.
You can purchase a PWM filter in between your camera and your camera connection. You can get these filters on Amazon for next to nothing.
Also, make sure your camera monitor is not set to cycle between camera's. It needs to be set not to cycle, i.e stay on the same camera without trying to cycle.
I am in need of 12V DC in the cabin for a Furrion RV rear camera monitor. Has anyone else got this accomplished in my 2025 2500 HD LT. I am done looking at the fuse panel under the steering wheel, but could not find 12V switched power. My next step is a deep dive under the hood and see if I can find and switched power in the fuse box on the left side in the engine compartment.
Has anyone else been successful doing this on the 2025 2500HD? If so, I'd be grateful if you could share.