Trouble installing SwiftKey via APKPure I don't have a Google account and use APKPure (and F-Droid) to get most apps I need. Now, there are a few apps which, after download, refuse to install - they give me the "App not installed" error when I try to install them from within the APKPure interface. Right now I'm seeing this with the SwiftKey Keyboard application: I already use it, and I'm trying to install an upgrade of it but getting that error.


How can I determine why I'm getting the "App not installed" message?
Should I try installing in "Safe Mode"? I've heard about it but don't yet know how to get into it.
If I want to try and install manually - where do I find the APK file(s) for my app?


Additional informations:


I'm using a Xiaomi Redmi 3S with Android version 6.0.1.
SwiftKey is already installed and is in use; but just to be sure, I replaced it with another keyboard as the chose/active keyboard app and the results are the same.
The APK file seems to be this one (assuming I get the same file from my desktop and from my APKPure app on my Android device).
$ apksigner verify SwiftKey\ Keyboard_v6.6.9.32_apkpure.com.apk 
WARNING: META-INF/DEPENDENCIES not protected by signature. Unauthorized modifications to this JAR entry will not be detected. Delete or move the entry outside of META-INF/.
Following @Izzy's patient advice in the comments, I got impatient and finally resolved this.

The reason for "App not installed" in OP's case

The pre-installed version of the SwiftKey Keyboard app had some sort of incompatibility with more recent versions - a "signature mismatch" - preventing an upgrade from the former to the latter. 

Should I try installing in "Safe Mode"?

Not relevant in this case.

So how do I upgrade SwiftKey?

Uninstall SwiftKey (just the main package; there may be auxiliary packages) and install the new version.### How to determine why you get "App not installed" generally

It's tricky. What you can do is have a look at the "logs":


Install a log viewer app like CatLog
Install something like Termux (or an SSH server, then SSH into your phone)
In a terminal, run adb logcat
Try installing SwiftKey
Have a look at the what you get in the log


You need to redirect the log output into a text file if you can't scroll your terminal well enough.