Android - Stuck on Download Pending in Play Store after Updating to Lollipop
You need to clear the Play Store data following these instructions.
From the Settings app, choose Apps.
Choose Google Play Store from the list of apps. A new screen will appear.
Click Force Stop.
Click Storage and then Clear data.
At the top right, click the three dots, then Click Uninstall updates to revert to the original version of Play Store that came with the phone.
Follow the same instructions again for the Google Play Services app, but this time use Clear cache instead of Clear data.