[GRASS-dev] addons list empty

Hello,
we have some problems with addons download in Grass 7.8.6 legacy.
The menù command “Install extension from addon” produce an empty list.
If we try to install extension from command line I obtain this:

g.extension extension=r.diversity operation=add
Downloading precompiled GRASS Addons <r.diversity>…
ERROR: Cannot open URL: http://wingrass.fsv.cvut.cz/grass78/x86_64/addons/grass-7.8.6/r.diversity.zip

but if I paste the repository addres sin a browser we correct download the zip file of addon, i.e. the addon exist, but Grass can’t download it.

How can I solve this?

Thanks, Francesco