I’m trying to set up a server on my personal machine for perforce (Helix Core). I’ve used noip.com to create an address to log into, and on my Asus router I’ve enabled the DDNS as per these instructions (https://www.noip.com/support/knowledgebase/setting-ddns-asus-router), but I get a warning “The wireless router currently uses a private WAN IP address. This router may be in the multiple-NAT environment and DDNS service cannot work in this environment.” and my programming partner cannot log into the server. They get the following message:

Connect to server failed; check $P4PORT.TCP connect to SERVERNAMEHERE:1666 failed.connect: 10.X.X.X:1666: WSAETIMEDOUT, A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.

I already forwarded the port 1666 on my router on both UDP and TCP as I would when forwarding ports for a game server, but when I check to see if the ports are open using a website like https://portchecker.co/ it says they’re closed. The weird thing is that it says my gaming ports are closed, but I successfully play games with my nephew all the time on a private dedicated server hosted on my machine, so I know the ports are open. This is beyond my very limited knowledge of how to fix it. I appreciate any help.