After adding two table on my SQL database I got this error :
All partitions using DirectQuery mode with Full DataView must query the same data source
It appears that the newest version of PowerBI Desktop don't support any difference on the database when you want to modify an old report.
I was using this release :
2.57.5068.721 64-bit April 2018
So I roll back to an oldest version :
2.53.4954.621 64-bit December 2017
And now everything works fine. I don't know if it's a bug or a feature, but It's quit annoying that I can't use the latest release of PowerBI Desktop