So you try to manually add a new user but the dialog for that disappears after a second ? If so, than I have the very same problem. Also log out and register a new account does not work, as the final submit button does nothing ..
@0xA4B16 Noticed the same after your comment. I am noticing site connectivity issues from certain users. Going to change a datacenter location and fresh install and attempt to recreate.
Made a fresh and clean nodebBB installation on a mini VPS, and with v1.12.2 all works, normal user registration, or ACP user creation works. With 1.13.1 there seems to be something wrong as it worked like 1-2 weeks ago or so.