I do have a set which I used last year so I could quilt one handed.they worked very well only problem I had was that I needed a larger area to FMQ in. Embroidery as no problem.
I would say the problem is the sewing machine , so check it is sewing .
Now look at the tautness of the fabric in the hoop. Is it too tight and the needle is bouncing off. Or is it too slack and the needle is not finding bottom area.
PM if you want.