Hi there, This was the error:
Error Details
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An error of type E_COMPILE_ERROR was caused in line 25 of the file /home/wpappson/public_html/crosslinkacademy.online/wp-content/plugins/wp-user-manager/vendor-dist/psr/http-message/src/UriInterface.php. Error message: Cannot declare interface WPUM\Psr\Http\Message\UriInterface, because the name is already in use
However, I have just installed version 2.9.4 and it is working again. Thank you so much