If you try to directly use the GUI flash programmer, or the command line flash programmer, but have not activated your LPCXpresso license, then you will see an error such as:
53: License does not permit flash operations from the command line
In such case, activating your copy of LPCXpresso should solve the problem.
If the LPCXpresso IDE indicates that you have activated, but you still see this problem, the the debug driver is failing to find your license. There are a number of reasons why this might happen. For details of how to solve such problems, please see the FAQ: