You have connected from different IPs, but did you do this from the same work station (i.e. PC)?
When logged in, the plug-in sets a cookie, so that you can log in more than once from the same work station. The connection IP doesn't matter.
You can switch this off by setting the plug-in to 'strict mode' in its configuration (Plugin Parameters back-end).
Just to be sure: log out all instances before you change to 'strict mode'.
Only Once! does not affect Super Administrator accounts, these can always have multiple log-ins. So make sure you test with a non-Super Admin account.
Please let me know your results.

I have logged in to site with remember me at seperate times on different IP's, simultating people sharing user names, and unless the people logout ( which most never do) people just click on saved favorites to go to the site are they are logged in.

I verified that there are multi sessions in the en4gd_session table for the same user.

Is there something that I have set up wrong that it does not check the sessions that exist ?

If I log out of any connection, than try to log back in the ONLY ONCE! stops the connetion but that is very rare that people log out, as that is one of the selling points of the site is that you don't have to log in everytime you connect.

Any suggestions?

I am trying to stop the sharing of user logins BUT still be friendly