Did you receive an email that looks something like this?
WHY DOES THIS HAPPEN?
This likely occurs when someone manually deletes the sync pair in CCB or Mailchimp, we can’t sync the data. Those pairs are broken.
Someone from your end is likely manually deleting/archiving one of the sync pairs which continues to break the syncing for those items. Even if they recreate the same data sets using the exact name, our program wouldn’t know as we look for IDs.
Please look at what is broken and check with those who have access to either your CCB or your Mailchimp accounts to figure out the flow.
To prevent any issues (e.g. overbilling), we require you to confirm and resave your synced settings.
Here's a step by step (quick) guide on fixing this issue
2. Click on Sync
3. Click on CCB to MC main tab
4. Click on Fix Now
5. Click on Select Audience
6. Click on the "replacement audience"
7. Click on Select MC Groups
8. Click on the "replacement group"
9. Click on Save
Don't forget to click on SYNC NOW to update everything or wait until overnight syncing happens.