Kegerator and Almost Empty Keg

Commercial craft brew keg, tapped it and went through about 4/5 of the keg, then untapped it and let all pressure out of keg using release valve (don't ask why was trying to fix foam)

My question is this, I put the keg back on but can't get it to dispense, is this because there is no co2 left to pressure the keg (after I drained it using valve), or is it because it's not possible to retapp with this little beer left.

I tried to re-pressurize at 12 psi for 24 hours but nothing happened, beer still won't dispense.

New to kegerators, so appreciate the help!

You should be able to pump the keg dry. Make sure that you reconnected the coupler properly. When you added CO2 again did you hear it going in to the keg?

I may have just solved the issue, has a low profile d-coupler which you need to push down on to start the co2. Wasted a few beers but seems sorted now.

Thanks for reply