There are a multitude of reasons for the top thread breaking.

Usually, this happens because the threading is not done properly.Try to re-thread the machine.

Examine the snapped thread,  if it is a frayed snap, rather than a straight cut, it is usually a rough spot around the bobbin case, race, hook or needle plate area.Run your finger around the shuttle area and feel for anything sharp, if you find something, however small, polish it away with fine emery paper.Find the rough spot and rub it away with some fine emery paper.

Sometimes it may be due to a knot in thread or because of old thread or low quality thread.Always run your machine with a good quality thread .

Incorrect needle size/type for project or if you have a blunt or bend or even a too sharp needle. You can try changing the needle – go up one needle size or try a Top Stitch needle.

Adjust tension. If the thread tension is too tight the thread may break. Make sure your tension dial is not too tight, it should usually be around the middle of the dial..

If the thread is caught on spool pin the thread may break

Did you thread the machine with the presser foot raised.

Make sure thread and needle are compatible.Thread too thick for needle, needle too fine for thread can also cause problems.

Starting to stitch very fast also can cause the upper thread to break. Make sure that all the procedure is followed in threading the machine..

If you have recently changed a needle, check you have put it in the correct way.Make sure needle is properly inserted