I have a white sewing machine, model 955. the knob on the side that controls the needle going up and down is really tight and doesn't move well. Also, when I step on the foot pedal it makes noise, but doesn't move the needle.

SOURCE: Needle doesn't move the problem isn't the foot pedal

Same problem with my 400. I took it in to dealer and they said main computer board on my machine would have to be replaced. Fortunately, they agreed to get it fixed for me. My machine is 2 years old. How old is yours? I wonder if this could be a manufacturer defect on the machine? Maybe this needs to be addressed with Viking Husqvarna Corporate.

SOURCE: my machine has power, but foot pedal only makes needle go slowly

sounds like the contact in the foot peddle has failed try a new peddle

SOURCE: Needle won't move

Please push the bobbin winder back to the left position and it will release the bobbin winder. Then you should be able to sew. If the needle won't move, you will need to tighten the turning wheel on the right side end of the machine. This should move your needle. Then you should be set to sew. This should help, it helped me!