App not installed with no reason why

Question

I have an Android app that have 2 different package name, one for the production environment and the other for development. The package names are

• com.example.app
• dev.com.example.app

The production version is always compiled with the same signature that we publish the app with to the play store.

The development version is being compiled with the developer signature that it gets automatically from Eclipse. Since we have 2 Android developers each version can get one of the 2 signatures of the developers (I know that we can set one signature for both of them, but it is not important for now).

When I'm trying to install the APK (through Dropbox) and I don't succeed I'm assuming that the problem is since I have a version installed with the signature of the other developer, so I'm uninstalling the app, and trying again. This tactics worked very good for me till recently.

In the last few weeks, I can't install the APK from Dropbox even after uninstalling the previous version, it just says "App not installed."

The only way I can install any of the versions (even ones that worked once) is by running it straight from Eclipse. All the other people in the company does manage to install the app through Dropbox.

Few things to clarify:

1. The "Unknown sources" is activated
2. The "Developer options" are enabled as well
3. It happens also with APK that did work on my device in the past
4. Other APKs that I'm trying to install do work fine.

Does anyone have any thoughts on how to solve this issue?

EDIT

To answer some of the comments, and telling what happens since then.

1. The version code is always the same or higher, so there shouldn't be and problem with that.
2. Those are not the actual package names. The package names are unique, and no other app is installed with those names.
3. I'm using Dropbox since every time one of the developers is uploading an APK for testing new features before they are moved to production, they upload an APK to dropbox and all the eam install it from there. I haven't had any trouble till recently. Another 6 people from my team have no problem with it even today.
4. Suddenly after more than 15 trials, just before testing if the ADB approach (from the comments) is working, it worked through Dropbox. I didn't change anything and have no idea what happened. I'll update if it will happen me again.

And few clarifications:

If I can't install the app on top of the previous version, I uninstall it which means, that the following things doesn't matter:

1. The version code doesn't matter
2. The package name is not being used (I just uninstalled a previous version with the same package name)

Thanks

Answer 1

Are you using Lollipop? if yes, try the following steps in order to uninstall the app (3 options):

Option 1: (Only valid before you uninstall your app)

• Go to "App info" of your app (Settings -> Apps -> your app)
• Touch the overflow menu icon and select "Uninstall for all users"

Option 2:

• Remove the data from your other users

Option 3:

• Uninstall the app in each of the other users

Pay attention to the fact that the app sometimes is installed under other users even when you don't install them under them explicitly. Didn't figure out the reason, but maybe related to the fact that the app is not installed from Google Play

I don't know if this will work, but i solved a similar issue this way :)

(i would have preferred adding this as a comment, but i can't due of my low reputation :( )