@Ruebezahl_001 

Hi, thanks for posting question in our community.

WAN IP should be a public IP address. The WAN IP is assigned dynamically by ISP. If the WAN IP address of the router is not a public IP address, but a private IP address, that means there is another NAT device connected to the WAN port of the router. You need to open the service ports on that device as well.

For most of the 4G LTE router, the internet service provider usually gives the private IP Address. So, if you want to do the port forwarding, please contact your internet service provider to assign you a public IP address or do the port forwarding in their part.

And I checked yours is a private IP address.  It is suggested to google if you don't know how to tell Public IP Address or Private IP Address.

For your reference: How to set up Port Forwarding feature on TP-Link Wireless 4G LTE Router.