Won't go!

[cdcmoto]

We bought a 2000 Gem e825 last week. My wife test drove it and it ran but the accessories did not work. The seller had a mechanic look at it and said that it wouldn’t be a quick fix. Then they lowered the price and my wife agreed because she only wanted it for golf so she didn’t need lights horn etc. I picked the car up (300 miles away) and when I got there the car did not run at all. I was told that batteries had not been charged and were dead. Since my wife had already driven the car I paid them and loaded it up. Next I plugged it in and let it charge over night. I tried it again and still nothing. Since I didn’t have a way of checking the 72 v system I checked each battery one at a time with a 12v tester and each was charged and held charge under a load. then I found that the accessories were now working but still no go. and no click when the key was turned. When you turn the main switch on the dash displays some numbers then goes dark. When the key is on the lights, turn signals etc will work. Next I tried the main switch I checked function and it worked but then tried jumping the two post, and nothing at first but when I was taking the jumper off I heard a click and the car worked. I then found that jumping the post wasn’t the cure but accidently grounding the post caused the click and started the car working. Even using an 18g jump wire from one of the post to the frame makes the vehicle work. What’s up with this. I then checked for loose or disconnected ground and found none. The key feels a little loose (not a firm positive feel). Would a poor ground in the key be my problem or should I look elsewhere?