If your app has a new version available from the App Store, it's important to get that update to make sure all bug fixes and updated features are available. However, it's possible that your phone won't let the app work.
For example, you might get a screen that says "Update":
But then when you click that Update button, it takes you to a screen that says:
This is a case where the customer used a different Apple ID to sign up for the app than what is currently being used on the phone. The customer will need to log out of their current Apple ID, and sign into the Apple ID they used when they registered for the wash.
To sign out of Apple ID and log into the correct account, follow these steps:
Step 1: Open the Settings App on the iPhone:
Step 2: Click on the arrow next to the customer's name at the top of the page:
Step 3: At the bottom of the next page, find the button that says "Sign Out" and press it.
Step 4: Have the customer re-enter the correct Apple ID associated with the wash account, and that should allow the customer to update the App and use it properly.