First of all, make sure the login page is actually asking you for your username. It's possible that someone changed it so it's really asking for your email address. If it's asking for a username then you can try a trick to reset your admin password.

I have attached a file that resets the Admin's password to just 'password'. Download this file and rename it to 'site_post.php' and then upload it (via FTP or your host's Control Panel->File Manager) to your '[root]/config' folder. Then try logging in using your admin username (I assume it's still 'admin') and use 'password' as your password.

If this is successful then remove the site_post.php from your site immediately and then change your admin password back to what it used to be by heading to Dashboard->Search Users and click on the admin's username and then the 'Edit User' button.

If this doesn't work, feel free to PM me and I can try other things.

Hi there,
Did you manage to get this issue fixed?
If not, feel free to PM me and I'll get it fixed up for you.

I am also having that problem, i got your file on my site and followed the steps, looking at the server files i can verify the username and password but still no luck.

What do you mean by 'looking at the server files, I can verify the username and password'?