Hi @tyankee,
i am confused, is this a review or a support question?
The error message you posted says you are trying to access the default demo or the Network Administration panel as this is the only site titled “WPAdverts Demo” all the custom demos are titled “Custom WPAdverts Demo”.
It just looks like you are trying to log in from an incorrect page.
How that happened I can only speculate you were already logged in to default demo as a user with login “user” and when you clicked log out button after creating custom demo you were redirected to the default demo logout page, and when trying to log in from a default demo with your custom demo credentials the error was shown.
This is just one possibility if you paste a link to the demo you created i could check if the demo was set up properly? That can be of course a problem with the demo creator, although it was used to create over 2000 demo sites and we did not have a similar problem and in the dashboard, i can see the users do login to their demo sites.
If this is intended to be a review then it is hard to comment, the whole premise of the review is based on that the plugin is not good because the custom demo creator is not working which does not seem to be true (at least based on what you wrote so far).
