Unable to upload new background image

I’m getting a form setup before I upgrade to a paid plan. I was able to upload a background in my earlier work, but I can’t replace it or upload anything new and keep getting the “An error ocurred while processing the media” error. The image is a PNG, tried with JPG and a different image, and tried on different browsers (I’m using Chrome but tested Edge and Firefox). Not sure if this is related to an existing issue, or if it’s on my end.