The external table does not have the expected format.

Since Today most of my Datasets do not update online - with Error : The external table does not have the expected format

The files dont have changed. 

But if i uplaod the same Desktop file with other name ( just a copy ) it works nice and i also can update it online. 

If u reupload the existing file it still gets the same Error. 

I cant uplaod all my datasets again and creat a hell of dashbords again...  

Any ideas? 

br

Chrisitan