I’m trying to set up my roku and my payment method is not accepted I keep being told my card can’t be accepted.
You don't really need to add a payment method. See this post for a good explanation:
Thanks for the post. I will do my best to assist you.
I would suggest trying to reload the web browser or use a different one to access http://my.roku.com. Do you have a computer you can access the website with?
In addition, please be noted that Roku Pay accepts the following forms of payment:
Keep us posted from there if you need additional help.