You can check to see if one of the pins on the 5 pin (programming) connector is not soldered by peeking under the edge of the board. You can reach under with a small soldering iron if its not.
Also make sure the pins aren't bent.
The IC in the top corner near the 12volt plug is the max232 rs232 driver. check the solder on it too. Also compare that all the parts are on , by looking at a working board .
Larry