There are four basic possibilities why your car did not start:
1. The jump starter might not be fully charged. Press the battery test button on the jump starter. All four LEDs should illuminate.
2. There might be a bad connection with the battery cables. Try the following:
a. Turn the big yellow knob on the jump starter to the OFF position.
b. Wiggle the battery clamps to help make good contact.
c. Turn the big yellow knob on the jump starter to the ON position.
d. Try starting the engine.
3. If the battery in your car is near 100 percent dead, or if the battery is defective, then it can suck too much power from the jump starter so that there is not enough power to start the engine. Do the dash lights come on? Does the radio work? If everything is dead then you may need something bigger than a portable jump starter.
4. If the engine cranks but refuses to start, then there might be a mechanical problem with your car that requires servicing.