What is the exact program you are using? Is it an official Google app or is it a third-party app?
Did you change any of your Google account security settings recently?
If it's a third-party app, you probably need to enable "Allow less secure apps: ON"
How do I unblock third-party apps? I tried to download to install Microsoft .NET Framework 3.5 Service Pack 1 from google notifier site. When it's an error aewwork 3.5 sp1 setup I must use turn windows feature on or off in the control panel to install or configure microsoft framework 3.5 sp1. What do I do now?