Uncheck "Enable MercuryMover" and recheck it in order to restart the MercuryMover service.
When you see this message, MercuryMover will open the Universal Access Preference Pane. At the bottom of this Preference Pane you will see the "Enable access for assistive devices" checkbox. Click on this checkbox. Now MercuryMover will function normally.
MercuryMover runs in a fully functional demonstration mode for 30 days. This message means that your demonstration period has ended. MercuryMover can be unlocked with a license code available at http://www.heliumfoot.com/store.
When you purchased MercuryMover, HeliumFoot (the makers of MercuryMover) e-mailed your license code to you. Try copying and pasting the e-mail address and license code from that e-mail into MercuryMover.
You are using a test version of MercuryMover. Please go to http://www.heliumfoot.com/mercurymover and download the current shipping version of MercuryMover.