Free 3 month subscription to Apple TV

I activated my free subscription a few days ago

How, and on which device? Did you get the confirmation email? Is the subscription listed in your overview?

but I am unable to view Apple TV. It wants me to sign up to a free 7 day subscription.

Verify that your Apple ID with the subscription is the active account on the device or Apple TV app, when trying to access Apple TV+ content.

Note that the Apple TV app also has other content that may require a different subscription. Subscribe to Apple TV channels in the Apple TV app - Apple Support