Bug? Apps won't install on Nexus5 (Lollipop)

Hi All !
I am developing an app since January and everything was working until today.
In the last two months or so when i was trying to install my app to my phone (Nexus5 with Lollipop) through B4A bridge sometimes i was facing in one problem: a notification windows appear on the phone asking me to upgrade my app. Well at the bottom of the window there are two buttons: "Cancel" and "Install". The "intall" button seems deactivated and I can't install my app. I can conly cancel installation.

I Found a strange trick to enable the "install" button by putting the phone in standy by pressing the power button and then waking up the phone. Very strange but everyithing was working.

Now neither this trick is working anymore and i can't install my app anymore on the phone.
On the other hand i can install my app without problems or tricks on a Samsung S2 (Android 4.1.2)

So my question is, how can i continue install/test my app on Nexus5 ??

Thanks in advance

Solution found!
Strangely the problem is related to a screen dimmer app installed on my phone.