Here’s what it says on the VDJ website:
The time limited full Pro trial built into limited (LE) versions of VirtualDJ may expire early if any of the following conditions are true:
You have already previously used a trial version.
You have used the 10 minute VirtualDJ Pro trial built into VirtualDJ Home FREE
You have changed the time and/or date on your computer either accidentally or on purpose in an attempt to try to extend the trial.
You have used or previously used an illegal pirate version of the software. Use of illegal versions will immediately invalidate the trial. Please support the software and its future development by purchasing it.
You have re-installed the software multiple times.
Once expired, it is not possible to extend the trial. However, you can test full VirtualDJ Pro features in VirtualDJ Home FREE prior to purchasing for 10 minutes at a time. After 10 minutes it will revert back to limited mouse and keyboard control again, but you can restart the software as many times as needed to gain another 10 minutes.
Apparently your best bet now is to use the VDJ Home FREE version. It allows you most of the features of the Full Pro version, but will shut down after 10 minutes (you will have to start the software again to continue). The Home Free version should have full FX plugins instead of limited.