Not ready - Roon ARC was unable to securely access your Roon Core: 2 routers

Don’t assume. Yes, one might think so. In reality, not every router deals well with it and there have been numerous cases on the forum where this was the problem.

Thanks.

You normally need only TCP forwarded, not BOTH.
Shouldn’t “Source Net” have an entry? (I have no experience with DD-WRT)

I can’t see if UPnP is on.
Also check the Port Range Forwarding tab to ensure that there is no conflicting rule there

Check that the Roon ARC settings in the main Roon app show that it’s using the 55002 port.
Try clicking Reset in the Roon ARC settings in the main Roon app, sometimes it seems to help.

I missed this originally. With 2 routers you probably need two daisy-chained forwarding rules. One on the T-Link forwarding the external IP:port to the Asus, and on the Asus to forward it on to the Core. And the 2 rules must not conflict somehow.

Try something like this:

A ConflictInMappingEntry error also occurred here, also with 2 routers, and was resolved by daisy-chaining the rules on the 2 routers: