I have paid for other subscription on my Roku and My PIN is NOT Working and has reset it 9 Times
My PIN IS NO WORKING ON MY ROKU TO start any trails.....
All I can suggest is that after you change the PIN on the website ( https://my.roku.com/account/pin ), restart your Roku.
Settings > System > About
Is the email address shown the same one used to log into your Roku account where you are setting/changing your PIN?