Harry Bloomfield wrote:

Also check which side the thread goes through the eye of the needle -
your
manual should tell you the correct entry for your machine.

I assumed it went through from front to back, but I will check that
point. Thanks...

That could well be the problem. Many of the old black straight-stitch
machines have the needle set to thread from the side, not the front.
All of the modern, multi-stitch machines I've used, thread from the front.