Have an M1 Max MacBook pro, running the most recent versions of Monterey, LRT Pro 5.8 and most recent version of lightroom. For some reason just in the last 2 weeks, whenever I render a video in the same way I always have done (pro res), which is several times a week the MOV will not play after rendered. When I try to open I get a spinning wheel, using quicktime. It will not open in other applications either. If I render as an MP4 it just plays a black screen.

Did you by chance use different render settings? Try not to use the highest quality setting, just go one step lower. Try 422 instead of 444 - see if that helps.