My sewing machine is missing skipping stitches

Thread tension is too tight - Re set tensions.

Needle is bent or blunt - Replace needle.

Needle is not the correct type or size for the fabric being sewn.

Thread take-up lever has not been threaded - Re thread and check thread goes through take-up slot.

Thread is of a lesser quality and needs to be changed for the correct sewing machine thread to suit the fabric being stitched.