Paramount Plus is included in my Xfinity account but will not allow me to login without signing up.

Hi there, lgc1601! We appreciate you taking the time out of your weekend to post on our XFINITY Community Forum. As an avid movie watcher myself, I understand the importance of having access to a large variety of your favorite shows/movies. When it comes to Paramount Plus, the app itself would be a separate subscription from the Paramount channel due to being a standalone streaming service, while our Paramount channel is the traditional broadcast channel.
I would be more than happy to review your current subscriptions to check further into this matter for you. Please send our team a direct message with your full name, the name listed on the account (if different), and the service address associated with your account. I'd be more than happy to look into this for you.
To send a Direct Message, please click on the “Direct Message” icon in the top-right corner of the screen, next to the bell icon click the "New message" (pencil and paper) icon then type or select "Xfinity Support". Type your message in the text area near the bottom of the window and press Enter to send your message and initiate a live session.