Today developer SGK has updated his spoofer to bring support for 4.31 allowing CFW 3.55 to access PSN once again. Check out the release notes and the download link below.
Release Notes:
SGK Spoof is compatible with 4.31 ReActPSN and good PSN games online!
Make sure that you do not have to install Spoof
If you have one uninstall it
Download, SGK-SPOOF-4.31 and install via "Install_Package_Files"