[eridius]

I believe iOS updates the app associations when either the app is updated, or the OS is updated. If you don't update the OS and don't update the app, it doesn't fetch a new site association, which is why the problem didn't surface until the release of iOS 9.3.

[tommyd]

Interesting, I am fairly certain the problem didn't surface until a few days after installing 9.3 although I could be wrong.