My shatter barely moved

You turned the force up, scrubbed the moment, and the pieces shuffle a little and stop. Nothing errors, and turning the force higher does almost nothing.

The pieces are starting underground

This is the usual cause and it is not obvious.

Shatter has a ground height, and it defaults to zero. A shape built from a primitive is centred on its own middle, so half of it sits below zero before anything is thrown. Those pieces are already at or under the ground, so they are held there instead of flying, and the ones above barely clear it.

Seat the shape before you break it. With the underside at zero, every piece starts above the ground and the throw behaves.

Measured on a one-unit block: unseated, the result spans the same width at every moment from nought to two and a half seconds. Seated, it starts at exactly the block's size and grows steadily apart.

There is nothing to throw

Shatter moves pieces that already exist. Give it a solid and it has one piece, which it moves as a single lump.

Fracture has to come first. And if you merged the pieces back together for performance, do that after the throw, not before.

The moment is past the end

The pieces fly, fall, land and settle. Scrub far enough and you are looking at the aftermath, which can look almost like the original if they did not go far.

Come back toward the start. Somewhere in the first second is usually where it reads as destruction rather than as a pile.

It is moving, just not far

Force and gravity work against each other, and the ground stops things early. If you want pieces to travel, lower the gravity rather than raising the force: a piece that is thrown harder still lands at about the same time.