I created a new Dataset in a workshop from an Excel document in a SharePoint site. That dataset is available to be seen in the power bi service site. I can't, however, use the dataset from Power BI Desktop for a specific pbix file. It's simply not available to me, the creator, from Get Data > Power BI Datasets menu. I can, however, access it from a newly created pbix file through Get Date > Power BI Datasets.
I've enabled the preview capability for the document.