Weird login-problem only with Safari

Hi there,

anyone an idea how to fix a Safari-exclusive login problem turning up since today?
I am using UNLOQ 2FA for login, also WP Cerber to move the login URL. With Firefox everything works perfectly. But with Safari I can only access the login page and after logging in I get the 404 message
Not Found

The requested URL /wp-admin/ was not found on this server.
Any ideas? Thanks in advance