Welcome Annie Lynn.
A couple of things come to mind. Does it reverse on the Red and Green stitches? Do the Red and Green stitches stitch properly when you change your length and width? Do you have the stitch length dial in the yellow zone while trying the yellow stitches on the stitch dial?
When machines have set a while, it will sometimes take some repeated cleaning and oiling. Frequently dried oil or lint is hidden deep inside that take a while to work out. Perhaps it could be that something is not connecting or moving correctly on the cam stack.
Good luck on getting the stretch stitches to work properly.
Janey - Neat people never make the exciting discoveries I do.