error after change domain name

After completing the website design, I bought a domain and changed the temporary domain. Since then, the Ultimate Member pages stopped, and an error message appears
The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator at [email protected] to inform them of the time this error occurred, and the actions you performed just before this error.

More information about this error may be available in the server error log.

Additionally, a 500 Internal Server Error error was encountered while trying to use an ErrorDocument to handle the request.

The page I need help with: [log in to see the link]