Troubleshooting
APK Won’t Install: How to Fix
The error message tells you which of five causes you have. Match it first, then fix it — re-downloading rarely helps.
Match the message
| Message | Cause | Fix |
|---|---|---|
| Install blocked / not allowed from this source | REQUEST_INSTALL_PACKAGES not granted to the opening app | Grant install-unknown-apps to that specific app |
| App not installed | Same package already present with a different signature | Uninstall the existing app, then install fresh |
| There was a problem parsing the package | Truncated download, or minSdkVersion above your Android version | Re-download once; if unchanged, check the required Android version |
| Insufficient storage available | Not enough headroom for extraction and optimisation | Free three times the APK size and retry |
| App not installed as package appears to be invalid | Split APK installed as a single file, or a corrupted archive | Obtain a complete single APK rather than a partial bundle |
Work through it in order
1.Confirm the download completed
Compare the on-device file size with the size the page stated. A short file will never install.
2.Check the permission on the opening app
Settings → Apps → Special app access → Install unknown apps. Grant it to the file manager you are using.
3.Look for an existing install
If any build of the app is present, a differently-signed replacement will be rejected. Uninstall first.
4.Free storage
Get several hundred megabytes free. Near-full devices fail installs in ways that look random.
5.Verify Android version support
A build targeting a newer minimum SDK cannot be installed on older Android, and no retry will change that.
6.Reboot and retry once
A stale package-installer state occasionally causes repeat failures that clear on reboot.
Worth knowing: 'App not installed' after a completed download is almost always a signature conflict with an existing package, not a corrupt file.