Entropy

Image from Wikipedia

If your GT5 Prologue won’t connect to the servers (every time you start it) it almost definately means you haven’t applied the update. I had it happen to me that it didn’t offer me the update because I hadn’t applied 2.20 (PS3) yet - there are various ways this could happen, but to repair it follow the steps below –

1. Exit the game
2. Go to your Saved Data on your PS3
3. Delete (or read below) your GT5 save file
4. Start the game again
5. Download the update

If you really don’t want to delete your save game, you can copy it to a flash memory stick; then delete it and copy it back afterwards.

Other tips are to go to Options, Networking and change your NAT type to 2 (from 1) and to Clear the Cache in the same menu. However, I found only the steps above worked for me.