Still no word from Sony on the matter.
Today, reports of PSN users being unable to sign into the online service started circulating. There didn’t seem to be any reason for the trouble. Everything is updated, network is working, and the Plus membership is up to date, so why can’t you play?
Apparently, Sony’s recently updated PSN’s Terms of Service agreement is at fault. Users first have to agree to the new terms before being able to sign in. The problem is that the console didn’t notify anybody that this was the case, leaving everybody baffled.
You can find the new TOS agreement in the settings on your PS4, and it will also apparently pop up when trying to access the friends list. Even still, plenty of users are still having trouble, either stuck on a “Please Wait” screen or seeing error messages. For those users, try using the Playstation Mobile app, as you should be prompted to accept the TOS there as well.
Playstation has given no official word on the issue. Some users, including myself, haven’t been prompted with the TOS at all, and can still sign in just fine. It’s all up in the air at the moment, but hopefully this helps those effected.