If you find that hitting Update Status on a Marketing Cloud data stream results in the below error, this indicates that the user to which Data 360 is authenticated to Marketing Cloud has an expired password.
Processing Failed
We couldn't authenticate with Marketing Cloud API. Try again later.
Note: To prevent this issue, when setting up Data 360 for Marketing Cloud, an MC API User should be used, which is what the Marketing Cloud documentation calls for. MC API Users never run into this "expired password" situation.
Salesforce Help: Create a Marketing Cloud API User in Marketing Cloud Connect
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