After yesterday’s blackout, Steam servers seem to be having similar difficulties, but due to another reason. Based on Steamstat.us, the game coordinators and servers are down due to routine maintenance that concludes every Tuesday.
Video game coordinators such as the ones in CS GO, Steam and TF2 are not responding either, and will likely continue so until the maintenance is concluded. While the Steam Store, Community, and Web API are working correctly, other games are unresponsive.
If you wish to take a look at further details, check the Steamstat.us website. Steamstat.us is an unofficial website and is not affiliated with Valve or Steam.