I've recently found a new solution; I created a redirect page, and when it lands, it runs instagram://extbrowser and it successfully opens the link on an external browser that will then open the App Store

Yeah it's incredibly odd. It looks like some of you are now also experiencing the same problem. And correct, Android Instagram browser still works fine and opens up Google Play. But iOS Instagram browser fails to activate the App Store page. I hope this is temporarily... my current solution right now is a redirect page that if doesn't open the app store in a few seconds, a message pops up telling people to click on the ... dots and Open in browser.