Failure to form stitches

Question

I have threaded & rethreaded many times checking if this was the problem. also bought new needles today (Universal lasse). I really need this machine going because I know it does really beautiful satin stitch & I need to finish off some applique cushions I am making to sell for Xmas! It has been out of use for a few years but was serviced not long before it was stored. I have oiled it and it doesn't seem to have excess lint. Help!Julie-Anne Jones, Otaki Gorge, New Zealand.