If username and password is right the browser returns to cgi-bin/koha/opac-user.pl with prompt to login. In /usr/share/koha/lib/C4/Auth.pm in line 1394 return ( $userid, $cookie, $sessionID, $flags ); $userid is blank. If I comment out lines 1388 til 1391 unless ( $params->{do_not_print} ) { print $query->redirect( -uri => $uri->as_string, -cookie => $cookie, -status => '303 See other' ); safe_exit; } $userid is O.K. and the login works. But all point (like "change password", "personal data", ...) fall back to login site too. If username or/and password wrong the message show that in right way.
Is this in 24.05.00 or 24.05.01? You are using the local login (password and username stored in Koha)? Are any other authentication methods set up?
Closing as we are lacking information to recreate the problem. Please reopen with more info if the problem persists.