I have question

I have question about when i try to use this plugin to my site and when i login there is somebody using my site i cannot login
i think its my developer account
i cannot login because his account is there,

this is the message:

This domain has previously been registered with WPMU DEV by the user Albert(a******8@gmail.com). To use the dashboard plugin on this domain, you can either login with the original account (and upgrade it if necessary), or upgrade your trial to a full WPMU DEV membership.