My game will load fine, except for GFWL. It will not let me sign into it because it says "my product key is invalid", but I have a store bought version I bought yesterday. I've done everything to get GFWL to work that I could find. My computer won't connect to the GFWL client so it also won't let me sign in thus I cannot save games on GTA4 either. I have the newest game version, .NET 4, c++ 2010, updated my computer, the newest GFWL. I've portforwared and everything. Nothing has worked. My game will run fine with the Xlive, but I did not install that version into my GTA4 game. I wanted to play online. Does anyone know how to fix this issue? I've even ran it as an administrator, but GTA4 and GFWL client and GFWL still won't work.

if it's a key issue, then you will need to talk to R* support, no one here can help you with keys.

I believe there a newer version of GFWL that you need to download and install.  Go to R* and download/install the newest version of GFWL and then try running the game.  I think that is your problem.

 

DrDetroit