Wrong opening hours.
It sounds trivial. It is the single most common reason somebody arrives at a closed café, gets annoyed, and goes to the chain instead — and worse, tells other people. Bank holidays, the week between Christmas and New Year, the summer Sunday you decided to open, the Tuesday you closed for a delivery. Every one of those is a chance for a listing somewhere on the internet to be wrong about you.
You cannot control every directory. You can control the page that comes up when somebody types your name, and you can make sure it is right, because we change it whenever you ask and it does not cost you anything to do so. That alone pays for the site.
The rest of it — the menu, the pictures, the story of the place — is what turns a passer-by into a regular. But hours first. Always hours first.