I can get mine to spark 2 or 3 times if I just tap the connectors together like that- try holding it in place for 2-3 seconds, then try again; chances are it won't spark again....
..or it'll go up in flames.
If polarity is correct, then check the connectors are clean ( not blackened or pitted ) and the solder joints are solid. If the esc wants to commit suicide it will though- quite often it happens upon connecting the batts & turning it on, so just be brave...