Cannot access Paramount+ subscription

I purchased a 3-month promotional subscription to Paramount+ through my Apple TV app, but I am unable to access any of their programs. When I try to view a Paramount+ show or movie from within the Apple TV app, it keeps asking me to purchase a subscription.

I also cannot sign in to the Paramount+ app. The instructions I found online say:

On a mobile device:

1. Download the app from your device's app store.

2. Load the app and click on "Sign In With A Partner". Select Apple TV as your service provider.

3. Sign in with your Apple ID username and password

However I see no option for "Sign In With A Partner."

Hoping that someone from Apple TV can help me resolve this.