Edit: After half day, my wife’s Mac started having the same problem. I have then applied the solution that I found in the Apple
Google Re-Release Native Gmail Back On To App Store –
You aint wrong in thinking that this is the second time that Google has released their native GMail app. The first release around 2 weeks ago was a massive fail and they pulled the app with in minutes. Today we have heard from Google and seen in the app store that everything is fine now and Google has re-released it in to the app store
Two weeks ago, we introduced our Gmail app for iOS. Unfortunately it contained a bug which broke notifications and displayed an error message, so we removed it from the App Store. We’ve fixed the bug and notifications are now working, and the app is back in the App Store.