Mistyped username when setting up, now I cannot register with devolutions account

I'm rebuilding my PC. I installed the newest RDM Free. When I went to Register with Devolutions Account I mistyped my username/email address. It now passes that username to the devolutions site and I cannot change it.
I have uninstalled RDManager and reinstalled it. But it does not ask for the username again. Instead it passes that invalid username to the site and waits for me to register with an invalid email address that won't register.
I assume this username is in a registry entry or file somewhere. Can I get that location so I can change or delete it? Otherwise I cannot register this with a devolutions account.