A 530 error usually means the server is rejecting the login before the connection is fully established.
Not sure if this is related: SSL certificate is not trusted by the FTP client - Wappler General / Bugs - Wappler Community. This discussion shows that the problem has been fixed in Wappler 7.7.8 and the discussion has been unlisted. But it has not helped me. I now have to use FileZilla to publish my sites.
FileZilla gives me the option to bypass the SSL Certificate.