I am trying to upload a game I created using Quest 5.3. I have been able to do this previously, but now I get an error "404 - File or directory not found", which doesn't make much sense. My .quest file is 33MB. Not sure if there is a limit. Thanks for any suggestions!

Try updating to Quest 5.4. You may need to go through your code and fix some things that have changed with the updates though.

Updating to Quest 5.4 is unlikely to fix the upload error. Best thing to do is email me details about the error (which dorkyrooster has done) and I'll take a look (which I haven't done yet)