Jharra
I have a Roku Ultra that is connected via CAT5. All of a sudden Tubi stopped working and showing RO error. I researched issue and did basic troubleshooting. I rebooted the Roko, uninstalled Tubi and reinstalled Tubi. None of the fixes worked. I changed the CAT5 cable. no go. I unplugged the CAT5 cable and connected my Roku to my wireless network. Connecting to the wireless worked. For **bleep**s and grins I reconnected my Roku via CAT5 and setup the Roku for Wired . That worked until I rebooted the Roku. I connected it back to the wireless and rebooted the Roku. It is working. So the short of it is to switch the Roku to wireless (if you have a Roku Ultra not sure about the other models). Hopefully this might help other users having the same issue.
RandyFlagg(yes I'm a Stephen King fan)