Dolby Vision has gone purple!

I have a TCL 4K HDR TV that has had no problems with my AppleTV 4K. I went to watch something, and the display was tinted purple. The other inputs on the TV work fine, and taking the Apple TV out of Dolby a Vision mode takes it back to HDR mode. Running the HDMI test doesn’t report anything. I’ve swapped the cables out, and still purple with Dolby Vision.

Does anyone have any ideas as to what is happening and how it can be fixed?

Thanks,

Quentin