Virtuemart can't produce a resized image of a product

[visitmontaione]

Joomla ‎5.4.2 + template NEOTERIC
VirtueMart 4.6.4 11226

I have a problem when I upload pictures for the products.

When I upload, in product > images I see the image broken in the product image but I can see the preview. (see attachment)
The image url is correct but the resized url is not present.
/resized folder has 777 permission.

In few words, VM can't rewrite the miniature.

Maybe I have done some damage when I have via FTP manually deleted the images from folder images/virtuemart/product/ and images/virtuemart/product/resized

The problem is that, every time I upload a products image also if I create a new products, the images cannot be displayed in backend and frontend too.

How can I fix it?
Thanks for your help.