1: Make sure your using the latest GFWL client. Download from here:
http://www.gamesforwindows.com/en-GB/download/
2: If so then also make sure you have enabled the following Windows Services (and any dependencies):
UPNP Device host
SSDP Discovery
3: Make sure your firewall allows the GFWL Client & Lost Planet2 exes in its exception list. I disable mine totally its a pointless resource hog anyway no-one is going to hack you unless you share files on the same gaming partition (I don't share any files) even then its highly unlikely & OTT to have enabled!
4: Make sure you have the following router ports open for GFWL to use:
53 UDP/TCP
80 TCP
88 UDP
443 TCP
3074 UDP/TCP
http://support.microsoft.com/kb/937424
5: Run this MS tool to see what your NAT/UPNP status are:
http://www.microsoft.com/windows/using/tools/igd/default.mspx
If this fails go here MS have tech staff manning it 24/7 apparently.
http://forums.gamesforwindows.com/8.aspx
6: Are you trying to sign in with an Online Gamertag as LP2 does not work with offline profiles AFAIK??? This means you must register the game to your online account before it will let you play at
all.
7: Who is your ISP as many reset the NAT status to closed without telling you once a month when they reset your download useage stats!