Can you clarify exactly what you did a bit?
I will try. If it is still unclear I can try to add a photo as well.
My English has it's shortcomings, especially when it comes to the richness of words.
As you can see, the extension is composed by two main parts: a bridge-like part connecting to the bracelet, and its link-like counterpart connecting to the clasp. The two part's are then connected together with a small rod or pin.
In order to get that satisfying 'click' that holds the extension folded into place, there is a notch on each outside of the bridge-like part, and a corresponding groove on the inside of the other part.
I used a plier and tightened the small rod holding the parts together.
You can also try to widen the thin gap in the bridge-like part.
Both methods aim to get the notches hold on better to the grooves I mentioned earlier.
I hope that clarifies a bit.
Kin regards