Unable to get 2021 iMac to mirror my 2021 MacBook at 4480 x 2520

I used to be able to mirror my 2021 Macbook Pro to my iMac in Retina (4480 x 25200), power went out now the iMac can only mirror at 1920 x 1080 and Retina (4480 x 25200) isn't even an option. I've restarted and tried to reconfigure for hours and I'm stuck.