Sub Category problem on the backend

[Sphyncks]

Good day everyone,

I already posted this problem on the french side 2-3 weeks ago but still have no answer. Maybe I'll be luckier over here :-) My problem is as follow:

 

I created multiple categories and sub categories. I can see all of them on the back and frontend. My problem is when I creat a new product, I don't have access to the subcategories only the categories are available. When I click un the + sign, the waiting icon (little circle arrow) is showing up ant this is it. I've been waiting for an hour or so and the sub-categories never showed up.

 

Does anyone went through this problem before or is it only me?

 

Please help me.

 

Cheers