すみません、お金を入れたのに飲み物が出てきません。 — Excuse me, I put money in, but the drink didn't come out. (Vending · Machine, Formal — to staff, JLPT N4)

Gesture & etiquette

Pointing towards the direction of the vending machine while speaking.

Some vending machines have a "おつり" (otsuri - change) or "返却" (henkyaku - return) button if an item doesn't dispense. Try that first before seeking help from a nearby shop or staff.