Android - App Not Installed

Hello guys!
I Have an app in Google Play Store and i would like to update it with newer version but i have a problem.
I decided to test the new version so i uploaded it to my phone (Galaxy S5) but i already had the old version installed from Google Play so i decided to test if the new version would install properly over the old one and it showed "installing" and after couple of seconds it showed "App Not Installed".
I tried to change Install Location to Automatic as all people say from other posts but it didn't work.
Before 10 months i worked on the project on my old PC but now i am on my new PC and before a week i decided to update the game.
I suspect that it is something to do with keystore or alias but i don't know.
If i uninstall the last version of the game and install the new one everythings is fine.
Thank you

 

Also i would like to tell that i removed google ads, that i have installed 10 months ago and reinstalled it now.

 

And i have the original keystore but i sended it over the internet from my last pc to my new.
And now the AndroidManifest file is completly different from the previous one, because i deleted the Plugins folder and installed the new version of ADMob that created the Plugins folder again.