"You cannot install this app because another user has already installed an incompatible version on this device"

Question

Refer this , Actually your debug version of the app didnt get uninstalled properly

1. Go to settings > apps > downloaded app list
2. You can see the installed applications in the list (the application may not be in order. or may be towards the very end)
3. Click on the application,go to the overflow menu option
4. Click on uninstall for all users options

In my case I wasn't able to see the application in settings > apps > downloaded app list because I have already tried to uninstall it.

What worked for me was: adb shell pm uninstall com.packagename

I think my problem was because somehow I had installed the app on the Primary and Guest user and couldn't uninstall them from neither one.

In Redmi note3, the debug version of app was got installed on second space.
So Settings->Second space->Go to Second space. Uninstall the app.

If using from Android Studio 2.3 (and maybe above versions), at last step of Generate Signed APK window, in Signature versions: part, check both check boxes, then click Finish to generate APK.

If you are reading this than probably you tried everything (ie. uninstall,clean cache,clean second space etc which you can do in phone) and your problem is still not resolved. I faced the same issue and took me a day to figure it out. But I found solution end of the day. Here is what you have to do.

1.Open your app in android studio
2.Click on gradle(on right side corner)
3.go to app->task->install->uninstallAll
4.Click on uninstallAll
5.Boom problem solved!!!

For cross platform app such as flutter

If you are coming from cross platform such as flutter or react native, You will not see gradlemenu. To get that
a) go to Android folder then app .
b) open build.gradle file,
c) click on Open for Editing in Android Studio.
d) you should see gradle.Now you can follow step 3

Tried to check the above solutions but didn't help me.

Finally I followed the below steps to over come on My device( Asus Zenfone 2)

Settings> Users> 1. Owner 2. Guest

Clicked on Guest> Playstore> Uninstall the application(Option came up once you search for that application)

After un-installing went back to Owner(User) from Guest. Was able to install the application successfully.