You remember this clearly.
The app worked before.
Same phone.
Same app.
Same account.
Nothing about how you use it has changed.
What changed is the operating system.
After moving away from an older OS version, the app no longer opens.
It installs normally.
But when you tap the icon, the launch never completes.
This happens when an app was built around behaviors that older OS versions allowed.
Those behaviors can quietly disappear in newer releases.
Older systems were often more permissive.
They allowed broader background access.
They delayed certain security checks.
When the OS changes, those assumptions break.
The app tries to start the same way it always did.
The system no longer accepts it.
That’s why there’s no error message.
The launch is rejected before the app becomes visible.
This is not a reinstall issue.
It’s not corrupted data.
And it’s not user input.
If an app worked on an older OS version but won’t open anymore, the problem is backward compatibility.
The app hasn’t fully adapted to how the newer system expects it to launch.