What target board are you using? Is it an off-the-shelf board or one of your own design?
What debug probe are you using? Is it the original LPC-Link, an LPC-Link2, or something else?
What version of LPCXpresso IDE are you using?
Have you tried booting your board into ISP mode ?
If you are still having problems, can you post your debug log?
Regards,
LPCXpresso Support