Can’t query tag and post_type at the same time

I ended up using

'tag_slug__in'=>array( 'vedette-accueil'),

and now it works. How this is different from

'tag' => 'vedette-accueil', 

and how the later would transform the query so that the cpt was ignored, I may never know…but I would love it if someone told me.

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)