No style in product Edit page (Backend)

-- HikaShop version -- : 4.0.0
-- Joomla version -- : 3.9.0
-- PHP version -- : 7.1.23
-- Browser(s) name and version -- : CHROME
-- Error-message(debug-mod must be tuned on) -- : no css when edit Product backend page

Hello,

I have a display issue in the backend.
Hikashop > Product > Click on a product.

The page is white with the content, it looks like the css is not loading at all.
Something like (starting with the links):

• System
• Configuration
• Payment methods
• Shipping methods

I had to update JCE Editor.
Thank you for your help.