I have 3 older Roku Ultras doing this on every boot. They want you to set them back and link to your account. once you have done so, they work perfectly until you reboot them. On the new boot they all want to go through it again.
We have gotten 3 new roku premier's now and they are all doing the same. We have tried using a different roku account, same issue... we have used a personal hotspot to set them up but also having the same issue