Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at "url"

I fail to send a long string of characters to my app whenever running it on IIS. When running it through radzen it passes perfectly, but running it on IIS causes this error to appear.
Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at [big url). (Reason: CORS header ‘Access-Control-Allow-Origin’ missing).

This error only happens if the string is long, if a string is short, let's say less than 500 characters, it goes to the server with no errors.

Yes, IIS has a restriction on max URL length. You can look for solutions online.