Hi,
Could you post some screenshots of the WAN public IP you're getting from your operator? Are you sure that Mobile is set as Main WAN in the WAN configuration page?
Also, If you're sure that everything is alright with the IP you're getting and should work - check the firewall settings, not always HTTP remote access opens up the rule. In the firewall, you should find the rule in "Traffic Rules" called "Enable_HTTP_WAN" and make sure it's enabled.
EB.