The first time an app tries to access your site, the app asks for your approval. Then select "Allow" and the app will use location service information if necessary.
To do this manually for iOS:
Go to Settings - Privacy - Location services.
Check that Location Services is enabled.
Scroll down to find the app.
Tap the app and select: "When the app is used".
For Android:
Go to Settings - Location - App permissions
Scroll down to find the app
Tap the app and select: "When the app is used".