ICloud drive - file sync problem

HI! I'm using Numbers on my MacBook Pro and my IPhone 6s.

I'd like to put some spreadsheets on icloud drive. Therefore, I save the file in ICloud drive folder... ok...

Now, automatically, the file should be synchronized with the cloud so that it appears on my phone, no? Well for most of the other types of files, it works...

But for numbers, I see "Waiting for upload" (actually in french "En attente de chargement"), then it switches to loading, then again to "waiting..." and again and again... And that file won't appear in the cloud on other device.

Now, if I export the file to a XLS file, same folder, it works !

Has anybody an explanation ?

Thanks