I have been having the same issue since August. There are plenty of other people having this issue as well. Every day or so there is a post about disconnects or sign outs. It seems to only be affecting a small population of users....roughly 5-10%. It's not region restricted because people from all over the world have posted this problem on here. I have tried everything to fix this issue. Including all of what you have done. My conclusion is it's on Sony's end. There is nothing we can do to fix it from our end. The only thing to do is to get them to look at their servers and figure out what's wrong. I am in the process of filing a class action lawsuit against Sony very soon. If they do not get this fixed within a month. This is considered "disruption of service". Not allowing certain users to access online features inadvertently or not is breaking the ToS and is against the law.
I suggest all of you having this issue to follow suit.
Its been 5 weeks already and I'm tired of this. Whats the point of even paying for internet or Netflix if I cant even use it.
Bumping. I have absolutely had it with this issue, tried every method, climbed several himalayan mountains and not ONE of the wise old men could help me. I am one step away from attemtping a demon summoning if I think that it will help. Fix it, Sony.