If you have the app already installed and it is not launching when opened...search "Garmin Golf" in the App Store and check and see if there are any updates showing available for the app from the download page > If no updates and just "Open" is showing...uninstall and reinstall the golf app to see if that resolves the issue.
Are you trying to install the app for the first time to your iPhone? Confirm and address an alerts appearing > Check and make sure your iPhone has enough storage space available > Close any running apps so there are not a ton of apps running on the phone at the same time > Try powering your phone off and back to see if that resolves the concern.
You can contact Garmin Support or contacting Apple Support may also be needed to determine if any other factors are causing the issue with the Golf app launching on your phone.
