Why have I never been able to get the blur tool to work... need to know what the trick is.

Actually the OP means the blur "brush", the Blur Tool in the toolbar.

This is one of the original Photoshop tools, probably not much used anymore. But I actually use it quite a bit on masks (not images; not precise enough for that), and I have sort of the same problem. It doesn't seem to work.

It took me a while to figure out why. It simply isn't made for modern high resolution files. It works with very low radius. You'll notice there's a setting for strength in the options bar, but no setting for radius which is what we need.

Try it on a 1000-pixel image, and you'll see it works.