If uPnP fails then you can try this... After this, there is no need to enable uPnP on TP-Link anymore. Because it will now act as a bridge and PTCL modem will handle everything on your network.
How to Configure TP-LINK N router as a wireless Access Point? - Welcome to TP-LINK
What is NAT and Double NAT:
What is NAT
The number of available IP addresses on internet it limited. To get around this a concept of NAT (Network Address Translation) was introduced. With NAT only the router needs to have public IP address (also called Gateway, usually a DSL or Cable Modem). All devices behind NAT router have private IP addresses - usually starting with 192.168 or 10. These addresses are only valid within the router network.
A quite common example is a simple network with one gateway (say DSL or Cable modem). The gateway has a public (WAN) IP address and does NAT. All computers connected to this gateway get assigned a private IP address. The gateway takes care routing the data from / to computers connected to it. To make a computer connected to gateway accessible from internet a port forwarding setting is required. If the gateway supports UPnP or NAT-PMP protocol, Air Video Server can transparently setup the port forwarding for the user. Otherwise manual port forwarding is required (port 45631 / TCP).
This scenario represents a single level of NAT (just one router on network that does network address translation). Unfortunately it often isn't this simple.
What is double NAT
Double NAT is a scenario where multiple routers on network are doing network address translation. Common example is a Cable or DSL modem, to which a Wi-Fi router is connected. Both modem and router have NAT enabled. Computers on the network are connected to Wi-Fi router.
Even if port forwarding is setup on Wi-Fi router, the computer is not accessible from internet, because the WiFi router itself doesn't have public IP address. It has a private IP address within the network of DSL/Cable modem. There are multiple ways to resolve this, unfortunately none of these is a silver bullet. It depends on concrete network setup to determine which one is appropriate.
Try this and post if it works. If you have any other question PM me or post in Networking section (because this is going totally off-topic for other BF4 players).
PS:
And always remember (or make a backup of) your router's settings, just in case you mess everything up