Can you please provide us with more information? What channel are you trying to install? How many channels do you currently have installed on your Roku TV? Have you tried removing any unused channels, restarting your Roku TV, then trying to add the channel back again?
As a last resort, we would recommend removing any unused channels then trying to perform a factory reset on your Roku TV, then once your TV has been set back up again, try adding the channels to see if the issue is resolved.