The question is rather what kind of critical error this is. It should be in the error log of your hosting. The cause should also be recognisable there, which could be used to tell you a solution.
Not sure how to access that error log on my hosting.
The support of your hoster can tell you that.
If there is no error log, you can also put WordPress into debug mode. See: https://wordpress.org/documentation/article/debugging-in-wordpress/ – the support of your hoster may also be helpful for this.
Here is the error log:
[14-Oct-2023 16:39:40 UTC] PHP Notice: Undefined index: action in /homepages/43/d913024675/htdocs/clickandbuilds/TDPAcademy/wp-content/plugins/uncanny-learndash-toolkit/src/includes/class-frontend-login-plus-2fa.php on line 439
[14-Oct-2023 16:39:40 UTC] PHP Fatal error: Uncaught Error: Call to undefined method WP2FA\Authenticator\Login::is_user_using_two_factor() in /homepages/43/d913024675/htdocs/clickandbuilds/TDPAcademy/wp-content/plugins/uncanny-learndash-toolkit/src/includes/class-frontend-login-plus-2fa.php:443
Stack trace: 0 /homepages/43/d913024675/htdocs/clickandbuilds/TDPAcademy/wp-includes/class-wp-hook.php(310): uncanny_learndash_toolkit\Frontend_Login_Plus_2fa->wp_login() 1 /homepages/43/d913024675/htdocs/clickandbuilds/TDPAcademy/wp-includes/class-wp-hook.php(334): WP_Hook->apply_filters() 2 /homepages/43/d913024675/htdocs/clickandbuilds/TDPAcademy/wp-includes/plugin.php(517): WP_Hook->do_action() 3 /homepages/43/d913024675/htdocs/clickandbuilds/TDPAcademy/wp-includes/user.php(121): do_action() 4 /homepages/43/d913024675/htdocs/clickandbuilds/TDPAcademy/wp-login.php(1241): wp_signon() 5 {main}
thrown in /homepages/43/d913024675/htdocs/clickandbuilds/TDPAcademy/wp-content/plugins/uncanny-learndash-toolkit/src/includes/class-frontend-login-plus-2fa.php on line 443
Remove the directory /homepages/43/d913024675/htdocs/clickandbuilds/TDPAcademy/wp-content/plugins/uncanny-learndash-toolkit via FTP – this belongs to the plugin that is responsible for the error. If you want to continue using it, contact their support: https://wordpress.org/support/plugin/uncanny-learndash-toolkit/
Thank you for the response, I noticed that once I saw the log, I’ve already reached out to their support. Thank you for helping me find the error.