This is caused by:

1. Not having your iLok inserted into a USB port - Check that your iLok is inserted and the iLok's green LED is lit.

2. Not transferring your License asset(s) to your iLok.

a. If you are a Demo user, Login to the URS web site here: ursplugins.com
from the Welcome Page select "Request Demo Licenses"
Then transfer your Demo Licenses to your iLok.
Please see ursplugins.com
b. If you have purchased a license, please register your license. Login here: ursplugins.com and select "Register Products"
More info at ursplugins.com
3. The Pace Interlok extensions have not been installed on your system
Please download and install the Pace Interlok Extensions from here:
www.paceap.com and ReBoot your computer!

4. Quicktime must be greater than version 6.4
Please update your Quicktime here:
www.apple.com
5. The wrong version of our software was installed
(TDM instead of Native or vise versa)


How to re-set Audio Unit validations
To reset the Audio Units Validation :

For Digital Performer
Trash this file and then relaunch DP:
~/Library/Preferences/Digital Performer™/Audio Unit Info Cache
or
~/Users/current user/Library/Preferences/Digital Performer/Audio Unit Info Cache

For LogicAudio Pro
Go to the Logic application menu -> Preferences -> Start ->Logic AU Manager.
This will quit Logic and launch the Logic AU Manager application.
Find the plug-in in the list and click on the "re scan"
button in its row.