Apple TV offer on Roku does not work

I spotted an offer for my Roku for three months of apple TV +

So not having used apple products before previously i created an apple id/account in order to take adavantage of this, and to see if apple services were as easy to use, and ""just work" as rumoured.

The sign up process ends with the following sequence:

Authentcation required, please conitnue on your computer, tablet or device

Then

Connection not available , there were errors completing your action, please try again

So tried again, tried again a few days later, still the same

"Connection not available , there were errors completing your action, please try again"

And how can you contact applle by email to sort this out??