Date column not displaying correctly in Power BI when excel file loaded from SharePoint

[beesee]

I have created a dataset from an excel file stored in SharePoint. There is a date column in the excel file that once loaded doea not display as a date field in my Power Bi report. Why is this happening and how can I fix it?

nb: I had a previous version of this report which displayed the date correctly but the file/report link became corrupted so I had to rebuild the report. Now the column won't display as a date.

The field also displays correctly if I load the data from a local file on my pc.