Nope, I have CenturyLink as my ISP, and have no issues with any of my Rokus. So it's something with the CL router that is messed up. Not saying it isn't something that CL can control, but I'd log into the router/modem and see if there's any settings that might be blocking Roku access.
I have taken down and reworked about every aspect of the local network that I can. As I stated in my prior post, there are not any local connectivity or filter/firewall issues. Also, I do not think Centurylink is blocking access to the Roku servers. As I said, I can trigger a security message from the Roku API address using a browser. If you look carefully at what I posted, you will also see that I do not have a Centurylink router. At the location in question I have carefully pored over the configurations, I have swapped with different routers, different router firmwares, reset the dynamic IPv4 address to a new one multiple times, etc. As far as I can tell, the Roku servers have blacklisted the range of Centurylink IP addresses in my area.
The only things I can think of that I have not yet tried are temporarily switching out the DSL modem with a different make and model or setting up a virtual IP address with a VPN. I may swap out the modem next, but I seriously doubt that will reveal anything new. As for using a VPN, one is not otherwise needed at the location in question and it adds cost and complexity, so I would rather not do that if I do not have to.
I see you are in the Auburn, WA area. What modem and router are you using and does Centurylink provide native support for IPv6 where you are? (I am in the Albuquerque, NM area. I tried switching to an IPv6 address, but it appears Centurylink does not natively support that where I am, so no help there).