Do a factory reset
How would Disney be able to help with a Roku pay issue that you're having. Doesn't make sense.
Settings/System/ Advanced System Settings/Factory reset
This will remove all the Channels you added and settings and set it to the original state.
Its a bit drastic.
So try System restart first
I am having the same problem trying to add Disney+. I have tried the update page twice and still Roku asks me for a pin. I have tried both updating an existing PIN and not requiring a pin.
I went through the disney+ website and was able to enter my payment info then get into it through my roku.