Unfortunately, Support is the only place to get the backend data you need to find out what happened. It is totally possible there's a weird bug or your instance degraded and needs some sort of reboot.
Things to check
- Is the original Sales Alert email corrupted? Did you check this? Did you try replacing it in the flow with the cloned version that does work?
- What's going on in the Results?
- Are you sure you aren't triggering the campaign?
- What about the Form Fills - are you using embedded forms? Did someone change something on your site?
- Did someone change something in SFDC - esp the user permissions for Marketo?
- how many records are supposed to be synced?
- did you try testing creating a new record in Marketo and manually pushing it? What happens?
Sometimes you have to do this yourself before asking Support to get involved.
Thank you. I appreciate your check list. I was really trying to determine if I was isolated in my issues or if others were having problems too. The lights were out at Marketo support and I was feeling desperate for a little help or validation. Nothing changed in my environment and I want to get to the root cause (which I think is going to end up being a Marketo code defect around "Salesforce Campaign Sync" for custom channel types).