It asking me to pay 2.99 for the last two episodes of Big Brother and I don't know why

the last two episodes

Are you referring to S24 E31 (Sept 15) and S24 E32 (Sept 18)?

E33 or later of the US edition of the show have not been released yet.

I do notice a episode numbering discrepancy between iTunes Store and IMDb (shift 1), as iTunes Store skips E08. Not sure if that is reason for confusing the Apple TV app.

- Did you subscribe to Paramount+ with Paramount+ directly for use with the Paramount+ app ?

- Or did you subscribe to Paramount+ in the Paramount+ app (in-app sign-up) on an Apple device (with billing through Apple)?

- Or did you subscribe to the Apple TV app Channel Paramount+?

These types of subscriptions have differences and are not exchangeable as such.

If the Apple TV app can’t find the episode number with your primary content provider, then it may offer what it thinks is the same content from a different content provider. Then your preferred content provider (Paramount+ subscription) may change to the iTunes Store (buy) unintentionally.

Verify that your subscribed Paramount+ instance is still selected as preferred content provider in the Details page for the show in the Apple TV app, under How to Watch. Set it back to your subscription type if needed.

Try accessing the wanted episode not from Up Next, but directly from the Paramount+ Channel page, if you subscribe for the Apple TV app Channel Paramount+. Else access in the separate Paramount+ app if you subscribe for that.