That's a fine one, it's just the real, pound-shop, cheapies that are useless.
It needs UV light to set, so make sure the surfaces are clean; dust and grease-free and just add one tiny drop of glue, press the surfaces together, clear up any "seepage" (I really can't take that word seriously since Kenny Everett's shows
) from around the break and turn the uv light on it.
UV torches are avialable very cheaply and they're handy things to have, you can check for uranium in glass, check if your cash notes are real or not and follow trails of mouse wee. (should you be so inclined)