> Access to XMLHttpRequest at 'https://api.make.rs/projects/' from origin 'https://make.rs' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.
I then manually disabled CORS (I overrode it with an extension), and noticed it was failing again, but this time with an HTTP 413 to the API endpoint. I changed my image to something smaller (it was 3 MB), and it worked.
The CORS error was because the ‘request blocked’ response was a html page without cross origin headers.
Worth checking for that