When you have a moment please post some additional information including the name of your ISP as well as details about the router and other network hardware in use.
On certain ASUS routers, you may need to enable uPnP + Port forwarding in a few different areas in your router settings. Give this thread a read and let me know if it helps:
It was already enabled in all 3 places. No difference. It cannot connect.
I have IPv4 and IPV6 on. IPV6 with a dedicated fixed ip that is visible from outside but roon is using only ipv4 which when I check on cantouseeme website can’t access any port.
Thanks for the information. There are a few things going on here that should be mentioned:
Setting your machine to DMZ does put you at wider security risk and we advise against doing this if at all possible.
Because you still got this error after connecting your core to the main router, it points to your router being CG-Nat, in which case you may need to contact your ISP to request a static IP. You can read more about that from our help article on the subject here:
Please let me know if you have any additional questions here.