Could be a signal strength issue , if you have not already done so first thing to do would be power cycle the Roku as well as the router. If one still won't connect try moving it to the tv that works and see if it works there, if it does then it's definitely a signal issue.
Ashepherdson we appreciate your assistance.
RonMar40 Addition to what Ashepherdson mentioned, make sure your devices are within 15-20 feet of your router to have a better connection. I also suggest contacting Roku support for additional help.
We haven’t heard any updates from you. I’ll go ahead and lock this thread in 24 hours. If you still need assistance, feel free to start a new thread in the community and we’ll be happy to help.