I can't merge accounts.

Hello, I am logged into xfinity.com under Address #1.  I have an account at Address #2 that no longer allows me to login to it.  It will not allow me to reset the password and doesn't seem to recognize the id.  So, I am trying to merge Address #2 into one login.  However, when I try to add the second address, I see it in the pulldown, but I get an error when selecting it.  It says, "We don't recognize that address. Please try again."  I don't understand why Xfinity does not recognize the address when I am pulling it directly from their pulldown.  I spent 3 hours in chat with 5 different agents today, none of which had a clue as to how to fix this.  Please help me add this second account to my login.