This started at around 3am BST 4/7/17 for my otherhalf, she can log in but gets the disconnect symbol straight away and after about 5mins she's booted with the 90002 error.
She hasn't done anything specific prior to just logging into Quarrymill as she had just lvl'd her RDM to 60.
She plays on PS4 and I'm on PC and yet to get this issue, because of this we originally thought it may of been PSN however according to SE this morning that has been resolved.
This obviously is not a PSN issue, I'm concerned this may be due to the counter measures that have been taken in response to the DDOS attacks, if this is the case I hope it gets resolved soon as a lot of people are losing out on quite a substantial amount of game time. It's ruining the joy of game play even for me as I'm unable to play with my partner, we've looked forward to doing SB together and currently that's not possible to do due to this issue.
My partner has three characters on the Siren sever and not one is playable, the third most recent one however she was able to go through the tutorial last night with no problem and even played on her for good hour, but once she tried logging into it today it got the same disconnect symbol and then the error.
She has a character on the Chaos Data Centre - Omega and doesn't seem to have this issue there, she's logged into it this morning and it's running fine, no disconnect symbol and no 90002 Error.
(UPDATE)
Since having this issue me, my partner and our friends have transferred to a Louisoux, having not much choice in the matter, best thing we've done.
We can now all play together without disconnection issues as I can see it the 12th of July now and these attacks are still going on and these issues people are still experiencing losing out on major game time now.
My advise if you think your connection can handle it transfer if your able to, if not I hope this gets solved and soon.