Thank you for the inquiry!
To ensure the process of removing and re-adding the Netflix channel is successful, make sure to restart your device before adding the channel back in from the Settings menu by navigating to Settings > System > System restart > Restart. However, if it still has no dice and the issue is only with the channel alone, this is a good indication that there is likely an issue within that specific channel that will need to be addressed with an update from the channel publisher. Channels on Roku are created and maintained by each channel publisher. In this case, you'll want to reach out to Netflix support directly to share your feedback.