Hi, welcome to the forum!
If you go into Settings > UPnP, do you have this enabled? Make sure it's enabled, then make sure there are no rules set in Settings > Port Forwarding.
On the Host Filtering page, you'll need to make sure your PC has the 'Xbox Live' service. (It's a bit confusing I know, but the Xbox Live service contains all the ports you need to properly filter PC games).
With Strict Mode disabled on the Geo-Filter, do you still get a strict NAT with these settings?
Fine tuning guide - How to set up your Netduma R1 quickly with optimum settings. Includes: How to get your full speeds, opening your NAT & Geo-filter settings etc.
FAQ - Includes: How to play with friends using the Geo-filter, I can't access the router control panel, Wifi keeps dropping out etc.
Wiki - Main link to the Wiki, for everything else please search here or on the forum.
Current firmware version (1.03.6) - If you are on anything below this, follow the instructions carefully to upgrade.
Any other issues please make a new thread on the forum, thank you
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