Open the app, and click on the menu in the top left corner.

Check if "Require authentication" is on or off.
If on, the customer has to activate the charger in the app.
If off, the charger should start charging as soon as it is connected to a vehicle.

Check "Max current (Amps)". The standard setting here is 16 or 32 (depending on the installation).
You can slide it all they way to the left.
When the app has loaded (fields will appear grey shortly), slide the slider back to where it was.
This resets the Amp settings, and might fix a charge issue.

Make sure that "Scheduled charging" is not enabled. If enabled, the charger won't provide power to the vehicle outside of the given time period.
This is used to determine the chargers power supply to a connected vehicle in a given time period.

If all of the above is checked, ask the customer to restart the app. The app should work after a soft restart. If this doesn't help, the problem lies elsewhere. Check the article "Troubleshoot charger" / Escalate to 2. level.

Check charger settings in app (App)