cannot download software packages from patch source

In my environment I have a server 2012 with IIS role  and UMDS .

UMDS download correctly the patches from internet,

I export the patches to the IIS folder

VUM, installed on another server, is configured to download  patches  from IIS and it correctly downloads the definitions.

After creating a baseline, I attach it to one of my host but when I try to remediate it I get:

cannot download software packages from patch source.

It seems that VUM is able to download patch definitions from IIS but it's not able to download the patches.

Any idea?

Thanks in advance