Can you see webfig login page if you connect to browser via http?
If yes, then follow advice by @WeWiNet, every single usage graph has separate setting about IP addresses of allowed clients.
If not, check if /ip service print where name=www shows it active (i.e. not disabled and not invalid), that you're connecting to correct service port (configured is shown in the previous command) and that it's not firewalled (you said disabling whole firewall doesn't make a change). You may want to check the www-ssl service as well ... it's less likely to be active as it requires installation of a SSL certificate and not many router admins bother with that.