Hi.
First of all, sorry for using this thread, but the problem is exactly the same and since nobody checked this issue is the main thread you find on google.
The problem is as stated above, Login With Ajax displays “An error has ocurred”. This is the unknown error handler on the Javascript side, not the php class one.
The problem occurs when trying to log in with a user who is also a Sensei user. The data received by the ajax request is empty, but wp_signon is executed. At this point, LWA checks wether the received object is a WP_User or a WP_Error in a strange way, comparing strtolower( get_class( $loginResult ) ) against lowercase strings of this class names.
Thinking about it now, it may be that signon returns a subclass of WP_User made by Sensei. with is_a or instanceof this would be ok, but with this string comparison is possible to get an error if WP_User is not strictly the class used for the user returned by signon.
Please check this. I cannot provide URL since it’s a client site.
Thank you.