Hi @Amy Jandreau ,
Welcome to Microsoft Q&A!
Sorry for the late reply. This issue occurs because a fact table for a cube has one or more records that contain an attribute key, and this attribute key does not exist in the corresponding dimension table. This behavior may occur when you have not processed the corresponding dimension before you process the cube or when the underlying tables actually have mismatched data. If the "Value:" field in the message has no number after it, the fact table must contain null data. Please refer to this link to get the solution.
Best regards,
Carrin
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