I’ve purchased the pro yearly subscription and am currently on my 1 month trial and while it’s working fine on my Apple TV, it’s not registering on my iPhone and is asking me to uograde.
I’ve read that I need to enable family sharing to share with other users, but I assumed that devices that share the same account would all have pro access from the single subscription.
If your devices are using the same Apple ID, you should be able to simply tap the ‘Restore’ button found near the bottom of the purchase prompt to activate your existing trial or subscription on additional devices.
If you are using Family Sharing (different Apple IDs) you will need to use Trakt as described here.