Visit http://dn.odroid.com/GAPPS and download GAppsInstaller_lollipop.apk
Install
Rebooted and log in google.
Check Play store version.
If you Installed youtube app, You must update Google Play services too.
If you update Google Play service, You will go though this situation.
I do not have solution for that. You must reinstall android image.
Check Play store version like this. Play store will update automatically.
Fist Update Google Store and must update Google Play Services later.