Thank you for providing the login information. I checked the case and found out this error:
Error 500 is the internal server error which is not a good indicator of the actual problem. Kindly contact GoDaddy and ask them to give you the error log so that we will have the correct error to be able to follow up.
I already read your reply but I insist that there is something blocking the ajax.php to reach our server address on your hosting service provider and you need to focus on troubleshooting that problem.
Thank you for your understanding.