I have a TP-Link Deco X68 running at my In-Laws premises, initially it didnt work with UPnP so I manually set up Port Forwarding, it looks quite different from your interface but has been working without any major issues, here are my settings:
According to the diagnostics window on the Roon ARC tab it looks like you have run into a Multiple NAT issue.
Roon support will need the model of your ISP’s modem to start with.
Do you have your modem set up in Bridge mode.
Does your ISP use CG-Nat? (Apologies if you don’t know what this is).
Is your modem connected directly to your TP-Link Router?
It may take some time but if you persevere you will hopefully be able to get to the bottom of the issue.
Ben here with the support team, my apologies on the delay in follow up! I wanted to check in and see if you were still running into connection issues with arc.
@oneofmany is steering you in the right direction with next steps and questions. I’ll be monitoring this thread for your reply