Maybe it's still a tension thing...

Question

I just bought a used Consew 14TU 4-thread Overlock, and although the owner told me that it had been recently serviced and it was ready to go out of the box...it isn't. I've rethreaded it and adjusted tension...it might make one or two loops, but then the thread breaks or comes back through the machine. I'm lost as of now...oh, and she didn't provide instructions.