Does the issue only occur on the NBC channel or across other channels installed on your Roku device?
Have you tried removing the affected channel NBC channel and then re-install again? If not, we suggest starting there. In some cases, removing the affected channel and then re-installing it may help. Restart your device before re-adding the channel back in to ensure the process is successful. We recommend doing this through the Settings menu by navigating to Settings > System > Power (If there is no Power submenu, proceed to the next step.) > System restart.
Can you please provide us with more specific information about the issue you are experiencing? Do you encounter any error messages? Are all the other streaming channels operating normally? How long has the issue existed and what troubleshooting done to resolve the issue?
With detailed information, we will be able to assist you better.