The motor has locked up due to tangled thread or for other reasons related to thread delivery.

• If the thread is tangled, remove the thread tangled in the machine, and then rethread the upper thread.
• If the bobbin thread is tangled in the hook, remove the thread jammed and clean the hook. Reinstall the bobbin and bobbin case correctly.
• Check the condition of the needle. If the needle is broken, bent or blunt, replace the needle with a new one.