If there’s no service issues, check that the time and date settings on your computer are correct:
Windows 10: Select the Start menu, then the Settings / cog wheel option. In the Settings window, select Time & Language.
Windows 8: Hover over the top right hand side of the screen and select Search. Select Settings and type “Date and Time” in the search bar to find the Date and Time App.
Mac OSX: Select the time on the right hand corner and select date & time preferences.