Message saying "Your trial expired!"

You need to sign out of Talkatoo and then back in.

If you were on a 7 day free trial, and after it expired, you either purchased Talkatoo, or were invited to a multi user account with this same email address, and you see this message, it means that you have to sign out of Talkatoo and then sign back in.  This allows Talkatoo to check the subscription again.

This wouldn't prevent you from signing into any other computer, only one where you were signed in before the purchase or invite was accepted.