Paper size mismatch message

[Adrienne89]

I’m so impressed with all the posts that sound so patient in this forum. I have too many hours sunken into this issue with no resolution and these things are not at all my forte. I don’t think I’m going to be very good at explaining what I’ve already tried, but I’ve tried a lot. I want to throw my printer out the window but I haven't yet because what I really want is to be able to print.

I've started getting a Paper Size Mismatch error message every time I try to print something, and the only option given is to cancel the print job. This started a week or two ago. It's an HP Photosmart 7520. I use a MacBook Air and an iPhone, so using macOS (I’m not sure which version but updated and current). I use almost exclusively letter-sized paper and always have.

I've read earlier responses on this forum and also tried everything on the HP website troubleshooting list -  confirming the size settings in the software I'm using, powering the printer down completely, uninstalling and reinstalling the driver, using the apple printing software and then trying the HP app instead, adjusting the settings to other sizes and then returning to letter, etc.

In case this is a helpful clue to someone who knows what they're doing: I've noticed that from the tools menu on the printer if I ask it to print a report it still gives a Size Mismatch error, but also gives the option to continue the job. I can pretend I’ve changed the paper and then hit OK, and it prints the report just fine.

Thanks in advance for any help that anyone can offer. If you do answer, please imagine you’re telling an average fifth grader what to try.