The machine does not feed material
The stitch length may have been set to zero - Reselect the proper stitch pattern and length.
The presser foot pressure is set too low - Set presser foot pressure adjustment lever to "normal" or increase foot pressure.
The machine maybe set in button hole mode - set the machine to straight stitch
Feed dogs are in lowered position - Raise feed dogs.
Lint could have gathered under needle plate - Clean out lint from between feed dog teeth.
Other Answers in the Category "Sewing Machine Troubleshooting Guide"
11. Fabric puckers