Hi Kevin,
I have a few questions to help us understand this issue.
1 - Is Workspace on IBM Cloud or local?
2 - If local, what Workspace version is being used?
3 - I'm assuming you are modeler or administrator in Workspace, and admin in the TM1 database?
4 - There is a directory inside of the TM1 database directory where the file is copied into when it's dragged on top of the cube. I think this directory is named something like model_upload by default. Can you check this directory to determine if your flat file is present? I think the flat file is renamed with a UID (check the file timestamps in this directory to see if it matches when you did the drag and drop).
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STUART KING
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