please correct this mistake in the documentation, I am sure this drive a lot of people nuts!
From Cpanel, click on the "Parked Domains" under the "Domains" section:
* Under "Create a New Parked Domain" enter the domain name you want to add to your network.
* Click the "Add Domain" button.
* It should add the domain to the list of parked domains and under "Redirect to" it will say "not redirected". That is OKAY.
Now you're ready to do your domain mapping.
This will NOT work, unless you installed WordPress under your MAIN cpanel domain!
I would completely remove the domain parking advice from the doc. A better solution:
Let's I installed wordpress multi user under example.com, and I want to add mydomain.com to my network. Then I should add mydomain.com in cpanel as addon domain (NOT as parked domain!), but with the /public_html/example.com document root.
By the way this a great plugin, wp developers should merge this into core! If someone has more than 1 wordpress blog, then is plugin is needed! I don't know why it isn't in the core yet.