How to Access Install Instructions on an iPhone Follow
If app recipients don't see the installation prompts on their iPhone, it's likely they are viewing the browser in a "desktop website" view. App recipients can adjust this in one of two ways:
In the browser menu (the aA icon next to the address bar)
Click the menu icon, then select "Request Mobile Website"
In the Safari settings
Navigate to the phone's Settings (grey gear app icon), scroll down and click the Safari app then select "Request Desktop Website" and make sure the toggle is set to "Off" (grey)
If the problem persists, click the "Clear History and Website Data" from Safari's settings: