Getting the dreaded OLE DB or ODBC error: Exception from HRESULT: 0x80040E1D error during refresh.

After much trial and error, I finally figured out what was causing the problem.

The invoice dates in my source file (TXT) are formatted as serial dates:     42737     = 1/2/2017

This is intentional.  When I first set up the table, I changed the formatting of the serial date in Invoices 2017 to be 2017-01-02.  I guess PowerBI doesn't like it when you reformat dates and then try to refresh a table (which makes no sense to me).  However, I found that as soon as I changed the formatting back to a serial date, the table refreshes without incident.

What I did to get around this is I created another column called "Formatted Invoice Date" and use that for appearances.

Note:  The dates in my Calendar and Invoices 2016 were formatted as serial.  I never changed them which is why I never had a problem with refreshing those tables.