First of all, please ensure that you have shut down any previous debug session. You must close a debug session (press the Red 'terminate' button) before starting another debug session.
After doing this, make sure that no debug driver is still running in the background. Use the task manager or equivalent to kill any tasks called:
- redlinkserv
- arm-none-eabi_gdb*
- crt_emu_*
Then boot your board into ISP mode before starting your debug connection:
Regaining debug access to target MCU
If that doesn't help, please post your full debug log:
The Debug Log
Regards,
LPCXpresso Support