error: Domainmapping failed because the domainmap plugin is not activated!

Hi,

We're using Wordpress 3.1.3
We recently bought your new blog templates plugin, but everytime we receive following error:
Domainmapping failed because the domainmap plugin is not activated!

Then we have to manually change the site info's of all new created clone url's.

How to solve this problem?

We also installed this domainmapping plugin: http://wordpress.org/extend/plugins/wordpress-mu-domain-mapping/
but doesn't work either.

Thanks
Erik