PlayStation Network hasn’t been very stable recently, with it being the target of a DDoS attack a day before it was to undergo scheduled maintenance, and then going through with that maintenance last week.
And now, the dreaded NW-31201-7 error has shown up for those signing into PS4, which means that the servers may be unavailable. This doesn’t appear to be the case on PS3, however, as users are able to sign in there.
Let’s hope this isn’t another attack and Sony are able to restore service to the network soon. We’ll keep you updated, and you can keep an eye on the PSN Status Page (which currently says that it’s online, despite it clearly being offline).
UPDATE: Although sign-in on PS3 and PS Vita appear to be fine, it now says that PSN is currently undergoing maintenance on PS4.
UPDATE 2: Sony are aware of the issues and are attempting to resolve them.
We are aware that there are currently some issues with accessing PSN. Thanks for your patience as we work to resolve the issues.
— Ask PlayStation (@AskPlayStation) September 4, 2014
UPDATE 3: Everything appears to be working and in order. Carry on.