By the time you read this, maintenance on the PlayStation Network has already started. It’s scheduled to last until 3:50 PST, or 6:50 if you’re in the Eastern time zone in the United States. As usual, access to PlayStation Home and the PlayStation Store may not be possible during the six-hour maintenance period.
If you’re on the PS4, you may not be able to share or see the What’s New, Library or Live from PlayStation content from the console. Multiplayer sessions could be interrupted as well. Final Fantasy XIV shows me error messages before asking to close the application.
This maintenance is coming at a time when PS4 firmware 1.70 is expected to release soon. It will add a lot of long-requested features including HDCP off, pre-loading and expanded sharing functionality.
Source [PlayStation Support]