I subscribed to AMC+ through Roku when I had a Roku TV. That one went out and we went with a Fire TV… absolutely nothing is working to get my AMC+ back that I pay for. Is there a trick to this? Or do I need to cancel and subscribe through Amazon essentially paying double for this year?
Subscriptions through third parties like Roku or Amazon generally come with significant limitations, so whatever you do, don't go from subscribing through one third party to subscribing through a different one. It's always best to subscribe directly with the provider. That will let you use the subscription on any device you like.
As far as attempting to sign in on a non-Roku device, try going to the AMC+ website and enter the email address that's associated with your Roku account and then use their "Forgot password" option. This may get you an email to set your AMC+ password and then you can that password and email address to sign in on their website and other devices. There's no guarantees.
I tried this multiple times and it did not work unfortunately.
Take it as a lesson learned. NEVER subscribe through a 3rd party. Subscribe DIRECTLY at a service's WEB SITE to get the most flexibility. The only downside is that it may be a bit more cumbersome to log in, versus the auto-login with Roku or similar. Also, I mention WEB SITE because using a phone app or similar will often mean a big chunk of your fee goes to Apple or Google.