[Baertram]

I think eero is just an example here as it's the router's "brand" or something like that. The other user used that. He was able to see it got an software update and he needed to configure the website of cdn.esoui.com as allowed again in his router app/page.

So your router's brand and company will/maybe different. Just the connection issue happens maybe because of the router blocking that website all of sudden, or your ISP does (sometimes one gets assigned an IP address by the ISP which was used for malicious tasks by others in the past and you now got blocked "by accident" due to that fact. Restarting the router may help then IF you will get a new IP address assigned then -> quite usual in Europe as you get the same ip only for like 24h, but unusual in US and maybe NZ, as you often have a fixed ip address -> And if this is blocked somewhere, well, ISP needs to fix it then to provide you a new IP).