Though threaded when I operate the machine the needle
Does not catch the bobbin thread to make stitches.

Have you double checked that the bobbin is correctly loaded? They will fit but not work if its dropped in upside down.

A Brother machine for example is wound counterclockwise as you look at it from above... others might be different.

If it is in correctly...perhaps its time to pull that cover off and clean it up...you might have a piece of a broken needle or stray threads interfereing with its operation.

I'm also assuming you have the correct bobbin type....some machines are sensitive about having the correct type used.