hi
To shoot the trouble
1. test your LPC-Link2 on another board. make sure it is in good condition.
2. To avoid workspace old associations, create a NEW workspace and NEW project, test if it can be connected.
3. To avoid on chip program interruption, connect the target in ISP mode.
4. If all above can't solve the issue, try to use LPCScrypt to update LPC-Link2 firmware to Jlink firmware. Test if your target can be connected with Jlink interface.
please note. if your LPC55S14 secure boot is enabled, there is no way to enable debug any more.
Hope this helps,
Jun Zhang