Does it work when pushing in the start stop button for sewing, or is it only when you have the foot pedal plugged in?
Also what is the "88" mode that you have it set on?
Were you doing Free motion prior to it stopping?
Take out bobbin case, could be thread inside of the case,
Oil the "wick" in the center of the bobbin case area. Do Not take the wick out....it looks like lint (white) so DO NOT TAKE IT OUT. A few drops of good sewing machine oil is all you need.
Also, what model is this machine can't tell from the photo?
I hope you try all of the suggestions and let us know how you are doing today.
Diana in TX