Check the instructions on jazz2online.com
You need the 1.23 version of the game. I'm pretty sure you can download it from jazz2online.com. Then just follow fawfuls instructions.
I would suggest you get the 1.23+ pack as well.
Now I aint completely sure, but I think you dont need a serverpatch nowadays (it used to be you had to get a patch or meddle in the registry editor).
If downloading the 1.23 patch doesnt help, then I wouldnt know what else could be wrong. Some people have had router problems... I think. I'm not enough of a computer geek, so I can't say for sure.

In short:
1. download 1.23 patch
2. do what fawful said
3. If it works - get the 1.23+ add on for JJ2 - it can be mighty helpful
4. If it doesnt work: ask around the forum a bit more

When all else fails, call Andrea Pirlo, he can solve any problem.