An HTTP 406 error occurs when a web server cannot provide content that matches the specific criteria (such as file type or encoding) requested by your browser.
Security settings or specific server rules may block the delivery of archive files like RAR. What is a RAR File?
Ensure there are no typos in the link, as incorrect URLs can trigger 406 errors.
Switching browsers can resolve issues where one browser's "Accept" headers are incompatible with the server. How to Open the RAR File 406 Not Acceptable - HTTP - MDN Web Docs
If you are unable to download the file due to a 406 error, try these steps: