Slitherine

I have BotB on Steam and when I try to login to multiplayer, I get the message "Sorry you are not logged on, Please logon and try again". Any suggestions? Also since I have BotB on Steam, is it possible to get a Slitherine version of the software and try it directly on Slitherline? Thanks.

No, that's not possible and besides it wouldn't resolve your issue.
Contact support[at]slitherine.co.uk for troubleshooting your issue.