Are you on the latest 3.2 patch and if so which one ? If you used the 3.2 hotfix then that would be the trouble as that particular patch will not let you upload to Arena scoreboard . If you used the 3.2 through the launcher then that would be the one you need . Try adding launcher and register exe through your firewall .
This is actually as intended. Since 3.1 the arena scores for Steam are posted on Steam leaderboards instead of the leaderboards on our website. This change means we could stop using .NET Framework 4 for running the Steam version of witcher2.exe preventing the occurrence of all the .NET-related errors on Steam. It's the solution mentioned in the paragraph under the download button here.
