I have a 2011 HSE LUX and recently on my rear camera display a red triangle with an exclamation point appeared in the upper left corner and the grid lines disappeared. Anyone know what might be going on and how to fix it?

It's quite well known for one of the pins inside the camera to corrode and fail. You can quite easily check this by popping the camera out of its little mount.

Spray some electrical cleaner on it but chances are the camera has failed and needs replacing. A retrofit camera is available for about £80/$100. 2015 Range Rover Autobiography 4.4 SDV8