Call tech support with (what you plugged in directly which worked), and router. Swap them during the call, then clone the MAC and plug the router in. It's one of my (religious) beliefs not to lie, but I'm afraid it's one of the few times I've tried, in the past with Ch*****.
I can't promise you that you are correct that it's the ASUS router, especially if everything works fine for weeks on end then all of a sudden....