Two email addresses

I signed up online with my Gmail account when I purchased the video doorbell but accidentally in signed up on the app with my comcast email address. I tried to change my comcast address in the app to my Gmail but it said that address is already in use. I want to purchase the wyze plus for my doorbell but not sure if I should use my Gmail account (for the online doorbell purchase) or my comcast (the email I use to login to the doorbell app). The gmail address has my doorbell purchase in it so I don’t want to cancel that address.

Try logging out of the app and logging back in with hour Gmail account.
If it works you’ll probably have to add your devices to the app agsin.