There’s not a lot here that can go wrong. You *need* the reset override to be enabled, the capacitor in place, the chip oriented correctly in the ZIF socket and locked down, and power applied. If you’ve done all of that, and are sure that those portions are all good, what remains is most likely a bad connection somewhere– and there aren’t a whole lot of those to examine.
So, carefully check every pin on the bottom side of the shield, and make sure that there are not any dry, missing, or cracked solder joints.
For testing, Double check that
1. You’ve programmed the Uno with the ArduinoISP sketch, and see the pulsing on the “pulse” LED.
2. You have autoreset override selected
3. 0.1 uF cap between RST and GND.
4. Board selected is an appropriate type (nano w/328P seems to work fine on the ISP shield ZIF socket)
5. Programmer selected as “Arduino as ISP”
6. Your shield is raised up very slightly off of the Uno, so that there’s no electrical connection between the USB
socket and the ISP10 connector on the shield. (Or, use a piece of thick tape over the USB connector.)
And then select “Burn bootloader.”