Region : Argentina

Model : TL-WR740N

Hardware Version : V4

Firmware Version :

ISP :

Hi all, please help me with forwarding problems.
I m using WR740N router, connecting to local ISP (Starhub, Singapore) thru dynamic IP

The Lan/Wireless/Wan settings as follow:







Then I setup the forwarding to my laptop (ip 192.168.1.100) which is running IIS:




I m also using DDNS, my domain is eir-pos.noip.me :




Finally I change port number for remote management to 8088:




My laptop firewall has been setup to accept private/public connection to IIS service.
From testing, my pad and android phone are able to connect to IIS thru wifi on the same network.
Whether I used 192.168.1.100 or eir-pos.noip.me or the wan address, I m able to get the webpages to display properly.
However, when I take the android phone offline and connect thru 4g, I m not able to connect anymore. I get the 504 error!
What m I doing wrong?
I tried searching the forum but from what I read, I only need to enable forwarding, change the remote management port, and I m all set to go,
but that doesn't work for me, please help!