I'm working on some campaigns that we do basically on a weekly basis. This is one of the few where we add the recipients to a Salesforce campaign first and then use that to sync back to Marketo and send out the email. I was setting up my smart list the same as normal where my filter is "Member of SFDC Campaign" and then I pick the correct campaign name. First, I noticed it was weird because I had inactive campaigns showing in that list for some reason. I've never had that happen before. Then when I picked my campaign, it doesn't show any contacts/leads in the list. I've double checked Salesforce and it has all of the members already listed and ready. They were also all added yesterday so it should not be a matter of watiting for the databases to sync. Any ideas on why they aren't showing up?
Were any changes made to your Sync User's profile permissions? If so, this could have resulted in the campaign member object becoming invisible to the sync user an not being pulled into your Marekto instance.
You should probably log a support ticket in that case so that we can take a closer look at this. Please include the name of the SFDC Campaign and a rough timestamp of when you added the members to this campaign.