Check if the IP in the DNS1 box is 173.233.94.154. If so, change it to match the IP in the shots below depending on if you are on 1.7.x nightly or 1.6.0. If there is another IP in the box, check "What to do if..." section below.
You should now be able to connect again. If you cannot connect:
Change your in-game settings from manual to automatic following this video.
Connect using the edited connection following this video
What to do if the IP in your PCSX2 DNS1 box was different
If the IP is set to 192.0.2.1
This means you are using the Alternate DNS Setups. If that is the case, follow the guide again. Custom DNS values are also here for quick reference.
www01.kddi-mmbb.jp
208.72.237.15
kddi-mmbb.jp
208.72.237.15
gate1.jp.dnas.playstation.org
153.121.44.150
Now try connecting again.
If the IP is set to 0.0.0.0 (Auto)
Set it now to 208.72.237.31
Next, follow this video to change your in-game network setting from manual DNS to auto DNS
Now connect using the edited connection following this video.
