What kind of plug did you insert? If it was a pair of headphones, the speakers in the headphones will cause extra connections on your continuity tester. You have to use something like an adapter or a shish-kabob stick that won't change the circuit. Or a chopped off headphone cord. There should only be 2 pins that change on the audio out port. The audio in port (the bigger one) has no such switch to my knowledge, but I could be wrong.

I don't know anything about your experience with this stuff, you seem to be doing quite well. Here are all the combos to test on audio out, I'm not sure if this is helpful for you or not. There are plenty of electronics noobies here, whether you're one of them or not, you're welcome either way.

1, 2

1, 3

1, 4

1, 5

2, 3

2, 4

2, 5

3, 4

3, 5

4, 5