I updated my app to the Google Play Store last night. Before the update, my App version was 2.3. There was some problem in version 2.4 so after another 2-3 hour, I updated
In order to show an update in Google Play, your app either should have been installed through Google Play or it should be a system application.
If you have installed your application through adb or installed from other sources, Google play will show "Open" instead of "Update".