How to fix my sewing machine that wont sew a ziz zag right?

I bought a lil sew & sew by tivaz and it was threaded with material still atached that ws used to check the tention and stitches. However the ziz zag stitches (# 3,4,5) will not stitch right. I make sure it was threaded properly several times and tryed changeing the tention but still can fix the problem.