TRY THESE METHODS IN ORDER
FIX (1. " A Hard Reset Of Your Connection"
Turn off your PS3 and turn off/on your router and Turn on Ps3 and Attempt a Sign-in. This will get rid of any static entries that have not self flushed themselves in the devices. Once the PS3 boots up the devices should obtain fresh MAC and IP info Hopefully Fixing it .
FIX (2 "UPnP"
(A) IF your router supports UPnP then ,Disable , Save Settings , Enable and Save Settings . Then on your network connection settings Enable UPnP . Attempt a Sign-in .
(B) If your router does not support UPnP then in your Network connection settings Disable UPnP . Attempt a Sign-in
FIX (3 "Call Sony" (optional)
Contact customer support for your region. Link here You must login or register to view this content.
FIX (4 "Restoring"
Ok this is the serious one , Restoring your PS3 will wipe ALL data From it . It will make it look like it has just come out of the box . There are 3 Restorations on your PS3 .
(A)I Think the first one is called restore system Defaults . This will only wipe Some data eg. Game Saves and messages but it will not wipe the HDD Fully . First try this one of course and attempt a Sign-in .
(B)The next restoration method is more serious . When you select this one you will get an option For a Quick format or a FULL Format . Select Quick Format . This should only take a few seconds . When complete Attempt a Sign-in
NOTE:You will have to sign up for the playstation network again as it will have been wiped .
THIS IS VERY SERIOUS. This method will wipe absolutely everything off your PS3 . Exactly like the day you bought it . I had to do this and it took 10 hours and 53 minutes . So if you are looking for a quick fix , don't do this. You can back up your ps3 system if you like. What you need to do is select FULL format instead of Quick Format . it will take a while as i have mentioned but at the end you still will have the firmware you were originally on as this is not wiped . After this Attempt a sign-in and if it doesn't work i have no idea what is wrong because your PS3 is completely reset and that should defiantly have solved it .
If i helped please let me know . I'm currently Full Formatting my PS3 so ill let you know how i get on Tomorrow .
If You have any questions just quote me and ill get back to You .