You may have a broken wire (red or black) in the 9V battery clip or attached wiring. If so, the clip/wires will need replacement. Or you may have a broken black wire at the DC jack or Input jack, if so it will need to be resoldered.
If not, there are two switches that can interrupt juice from the internal battery. One is built into the Input jack, and the other is built into the DC power jack. If either switch is not making contact, you can run the pedal from a power adapter, but it won't run from a 9V battery.
Rubbing alcohol won't hurt the pedal guts, and may help clean the contacts. Remove the 9V battery and unplug the DC adapter from the wall. Drip a SMALL amount of alcohol into the DC jack, then run the adapter plug in/out of the jack several times. Do the same with the Input jack, except with your signal cable plug. Give the pedal 10 minutes or so to let the alcohol evaporate, then see if it powers up. Ok to repeat a few times.
If that doesn't do it, you'll need to check the wiring for the DC and input jacks, and possibly replace one of them.