Android App Downloading But Not Installing My Device is Motorola Moto G 1st Gen. running Android Lollipop 5.0.2

From the last 2-3 months, my phone is not installing apps. It downloads the app and even shows installing but never completes. After showing "Installing " for some time, the notification will go. If I go back to Play Store, it says "Install" and not Installing. So I have to repeat the same procedure.

I have tried clearing Data and Cache of Play Store, Download Manager, Google Play Services. I have over 5 GB space available on phone.

I have tried the above solution many times but it doesn't works. The only thing I don't want to do is factory reset.

 Update:  After I updated to Android 5.1, apps started to install properly so I think it was a bug related to 5.0.2
Try following the methods below:


How about you try installing the app by manually downloading it's apk which I believe, shouldn't disappoint you.
You must have "Unknown sources" enabled from Security option in Settings menu in order to be able to install APKs.(Settings>Security>Check the Unknown Sources option). 
For example, visit http://www.whatsapp.com/android/ and click on Download apk, when download is finished you shall copy the apk file anywhere in your SD Card or internal memory which you can access, or download the apk right-away in your smartphone. You your favorite file explorer(I use ES File Explorer) and navigate to the apk file location in your smartphone and touch to open it just like you would open any file and you will get an option of installing the app.
Power off your Moto G and reboot to bootloader by pressing Volume up + Volume down + Power button and you will be taken to bootloader, from there you should use volume down to scroll down to Recovery option. Use Volume up or Power button to enter Recovery mode and than wipe cache(do not execute wipe data as it will wipe the internal memory/sdcard) which can take 5-10min if on stock ROM. When done, reboot and post if you face the problem again.