Date column all null

Anonymous Omid_Motamedise PhilipTreacy 

Thank you for the suggestions. While trying some of your suggestions i stumbled across some more information.

This query is automatically email out from our systems every day. The query comes as a .xls 'Microsoft Excel 97-2003 Worksheet' and when put directly into power query as is, the accounting date column shows 'null'. However when i open the Query in excel, make no changes at all but simply save it as is, i am prompted with a message i have screenshot. 

Clicking continue saves the file as is. Then loading the same file back into power query, the accounting dates appear as they should be.

You may be able to see my problem already. I do not want to have to manually save this report everyday. I just want Power BI to be able to accept it as is and automatically update my report. Do you have any suggestions how i can accomplish this? What exactly is the issue with the original format? If i can have the report sent out a different way/format, what should i tell IT i need? Or maybe, is there something i can do in power query to fix this report automatically instead of resaving it in excel?