install manager not recognizing my new email

I tried to open install manage but it lists the email I was using up until a few months back and of course when I try to login with that it does not work. I tried to click on the + button to put in my new email but it then says I already have that duplicate account. There is no way I can see to change the email.
Please advise what I can do. Is there a preference file I can trash?
I am trying to reinstall the sql database file as nothing shows in studio
mac 10.11.6
thanks
Bob
Comments
If you use the + button to create a dummy account, which won't of course log in so choose Work Offline, you should then be able to highlight the real account and edit its email, then use that to log in and delete the dummy account.
Thanks for the idea. I actually do have two working accounts (long story) and I tried what you suggested without success. I could get inside the software but trying to change the main email did not work so I gave up. Instead I wiped the drive again and this time did not migrate anything from my old system; its all backed up and so I will install all my software brand new as planned without any tangled up systems. Problem solved.
thanks again.