App not installed
Android's catch-all failure message. It has no single cause — the useful information is in what the app was and what changed.
Why it happens
The system shows this when an install fails and the installer has nothing more specific to report. Behind it is usually one of the other errors on this page: a signature mismatch, a downgrade, missing storage, or an OEM restriction.
How to fix it
1. Was there already a copy installed?
If yes, it is most likely a signature mismatch or a downgrade. Those two account for most of these.
2. Is the device a Xiaomi, Redmi or POCO?
MIUI optimization blocks installs and produces exactly this message with nothing else to go on.
3. Use an installer that reports the real reason
The underlying error code exists; the system dialog just does not show it. An installer that surfaces the actual failure turns this into something you can act on.
Also shown as
- App not installed.
- Application not installed
- install failed no message