1)check if you have 24v between R and C. Voltage=0,?bad transformer; v=24, go to next
2)at the board, put a jump wire between R and Y (connect R & Y), condenser should be on since you have a new contactor. If not, bad wire between board and contactor.
3)jump R and G, blower should be on.
4)If 2) and 3) both are working, the problem is your thermostat or wire between the board and thermostat.