Hiya,
Can\ you put in a drawing of your programming circuit and the different signal levels?
Attached is the circuit I use for programming to the Segger JLink Plus (should be the same connections as you use) and the Segger Needle connector:

Just a couple of notes:
- /UC_RST is pulled up and has a voltage supervisor on it.
- EZP_CS_b is left floating
myke