On my subscriptions page it says I have a prime sub available, but the button doesn't show up when i try to sub to a channel. This was confusing and I tried it in 6 ways before figuring out the reason: i'm on an amazon trial account for the second time. I think it's reasonable that I don't get a prime sub right now, the issue is that my subscriptions page says I do. The channel menu performs the check for a prime sub correctly; the subscriptions page should perform the same check. (Also it might give the info why it's unavailable, this info was a little hidden on the prime gaming faq)

Maybe the same issue exists if prime subs are not available "in your region"? (I can't confirm this)