Thanks for letting us know about the issue you're experiencing.
Some customers have reported that changing or updating your account's payment method resolves the issue; therefore, we suggest you give it a shot.
Feel free to visit this Support article for instructions: How do I update the payment method for my Roku® account?
If after attempting the suggestion above, you are still unable to add the channel, you can try installing it from our website by clicking this link. Once done, run a software update on your Roku device for the channel to show up on your home screen. To do this, go to Settings > System > System update > Check now.
Let us know how it goes!
All the best,
Roku Forum Moderator