Was it sold as 'not working'? Were there representations in thel isting that it was a working camera? If someone says 'working' and 'no returns,' it needs to be working. I'd contact seller.
The counter will not work, period, with the back open. The silver pin on the right side needs to be depressed for the counter to engage.
I would jiggle that pin a bit, put a spool in the top chamber, and keep trying. With the back closed, a spool in the top chamber will make the camera think that it is loaded and will show you if it is working (it may be rough winding because of the ridges in the spool- no harm).
What's the lens, by the way? Yashikor or Yashinon?