Confirm that the needle is inserted correctly, with the flat side facing the back of the machine – may be it changed direction after the screw got loose. Ensure that it is securely tightened. Double-check the threading of both the upper thread and the bobbin thread. Verify that the bobbin is inserted into the bobbin case with the thread unwinding in the correct direction.

Some sewing machines, may have a built-in fuse for protection. Check the user manual for the location of the fuse and inspect it to see if it has blown. If the fuse is blown, replace it with the correct type and rating as specified in the manual.
Ensure that the handwheel is not in the “disengaged” position. Some machines have a disengagement knob that allows the handwheel to turn freely when winding bobbins. Make sure it’s in the correct position for sewing.

Incorrect thread tension is a common cause of loose stitches.A needle that’s too small for the fabric can cause skipped stitches and loose seams.A very long stitch length can result in loose stitches.Rapid sewing on thick fabrics can lead to skipped stitches and looser seams.

Check that the needle is in the center position and not offset to the left or right. A centered needle is essential for straight stitching. And that stitch width is set to 0

Check the electrical supply to your sewing machine to ensure it matches the machine’s requirements. Voltage fluctuations can lead to errors.

If the motor overheats due to extended use or sewing through thick fabrics, it may temporarily stop to prevent damage. Check that the power cord and foot pedal connections are properly plugged in and not loose. Ensure that the voltage supply to your sewing machine is stable and matches the machine’s requirements. Voltage fluctuations can lead to motor issues.

You will have to read through your sewing machine manual to see which lever you have locked. A damaged needle can cause the handwheel to become stuck and the machine will stop working. Check if the needle bar is moving correctly when you manually turn the handwheel.

Do not attempt to turn on the sewing machine again. Disconnect it from the power source, unplug it. Ensure that the machine is in a safe place and away from anything that could catch fire.If your sewing machine is under warranty, contact the manufacturer or the place of purchase for guidance on repair or replacement. Additionally, if you have insurance that covers accidental damage or electrical issues, you may want to look into filing a claim.

Ensure that there are no missing parts, such as screws, nuts, or washers that are necessary to secure the handwheel in place. If it is just loose, tighten it with a handwheel knob or a wrench. Make sure the handwheel is properly aligned with the spindle or shaft it attaches to. When reattaching it, align the notches or grooves correctly.

Some sewing machines have a thread release lever or clutch that allows the handwheel to turn freely for bobbin winding. If your machine has this feature, ensure it’s in the correct position for regular sewing and not in the winding mode.