I can't upload avatars of categories in a site.

Hi,

Thank you very much for your providing a good products.

I used Easy blog for some years.
I found I can't upload avatars of categories in a site.
I found the same problem in this forum but I could not find out what I should do.
https://stackideas.com/forums/how-can-i-change-categories-avatar
I do not have any option to select an avatar in the category editing page.
This problem does not happen in my other sites.

Do you have any advice to fix it?

I attach a figure.

Best,
Kenzo