There is a problem with the latest Sundance Now application running on my Roku Ultra. The application no longer allows the user to find their My List. And, when you try to add a program to My List an error message appears. Obviously, this application was not tested before it was released. Absolutely terrible testing by whoever is releasing this application!
Try removing the channel from the Roku home screen by navigating to the channel tile, pressing the * key on your remote and choosing 'Remove channel'. Then restart your device from Settings>System>System restart. Once your player starts up again, add the channel back once more. Does this clear up the issue you are seeing?
If you are still experiencing an issue, you'll want to contact the channel provider support directly to inquire further. Many channels on Roku are developed and maintained by the channel provider themselves.