Pickit3 Program Can Not Recognize Chip

Pickit3 program can’t recognize chip
Hello,can anyone here help me out?
The tip is given below:

Target Device ID (0x0) is an Invalid Device ID. Please check your connections to the Target Device.

It can be programmed after changing chip, and the circuit is no any problems.Here the original chip is also continue to work. But I don’t know why it can’t enter into programming ! The chip I used is PIC18F45K20.
This is the PIC18F45K20 datasheet: http://www.kynix.com/uploadfiles/pdf8798/PIC18F45K20-E2fMV.pdf Please look the details from it if needed.Can you help me solve it?
Thanks a lot!

What Digi product are you working with?

I would check the connections between the PICKIT3 and the PIC. Normally the problem is a bad connection, reset line included. If the connections look good, it is also possible that something else on the programing lines is holding them HIGH or LOW, or there is to much capacitance.