Notice it took 3 posts for you to explain what is actually going on so you could get a good answer.
I’d say the jumpers themselves are bad or you were just not getting good contact. Plus, if the battery was really drained, you would need to leave the jumpers on a while to bring the battery back. If the battery shows better than about 12.4 volts or more after it charges up a while, I’d say it is OK, but now you need to determine if you have a parasitic draw draining the battery overnight. If the PT has an aftermarket stereo, alarm (on a PT???) or remote starter, assume one of those is the culprit. If not, the task gets a little harder. Eric The Car Guy on Youtube has a good video showing how to do a parasitic draw test.