If you are using CS6 -
An Announcement from the Acrobat user-2-user forum:
Issue: Nothing happens when you launch Acrobat X 30 days after installing a CS6 suite.
Solution: Re-activate Acrobat through another Suite product:
- Launch another CS6 application, such as Photoshop.
- Choose Help > Deactivate.
- Follow the onscreen prompts to deactivate.
- Close the application.
- Launch the same CS6 Suite product again.
- EULA comes up. Accept.
- Sign in with your Adobe ID to register trial. Quit and re-launch application.
- Trial dialog comes up. Click on License this Software button in this dialog.
- Sign-in with your Adobe ID to register.
- Provide CS6 Serial number next. Click Next.
- Quit application.
- Now Launch Acrobat X
by David Kastendick (Nov 15, 2012)