Cannot see the content of my shared folder from my hosted OS ( $USER already in vboxsf and VM already restarted )

I have a Ubuntu OS running inside a VM made on Virtualbox.

It's some time that I cannot see anymore the content of my shared folder from my Ubuntu OS. I am loading content into the shared folder form the external OS: windows10.

I have configured the shered folder from virutalbox UI like so

The UI tells me as I try to access the sf_VirtualBox_cartella_condivisa_VM03:

"you do not have the permission to view the content of..."

which I understand, because Isee a red cross icon over the folder icon.

Then I have run

tommaso@tommaso-VM3:/media$ sudo adduser $USER vboxsf

[sudo] password for tommaso: 

but I get

The user `tommaso' is already a member of `vboxsf'.

I restarted the vm but the problem remains.

Inspecting the content of folder media, I get

tommaso@tommaso-VM3:/media$ ll
total 16
drwxr-xr-x   4 root root   4096 lug 31 14:56 ./    
drwxr-xr-x  20 root root   4096 lug 31 14:48 ../    
drwx------   2 root root 4096 lug 31 14:56 sf_VirtualBox_cartella_condivisa_VM03/    
drwxr-x---+  3 root root   4096 nov  8 15:06 tommaso/

So I have opened have opened another VM having the shared folder working, and I see that the permissions and user are different

tommaso@tommaso-VirtualBox:/media$ ll
total 24
drwxr-xr-x   4 root root    4096 giu 24  2021 ./
drwxr-xr-x  20 root root    4096 ago  2  2021 ../
drwxrwx---   1 root vboxsf 12288 nov  1 10:58 sf_VirtualBox_cartella_condivisa/
drwxr-x---+  4 root root    4096 nov  8 15:24 tommaso/

So I have tryed to "align" them manually by running:

sudo chown root:vboxsf /media/sf_VirtualBox_cartella_condivisa_VM03/

sudo chmod g+rwx /media/sf_VirtualBox_cartella_condivisa_VM03/

so that I get

tommaso@tommaso-VirtualBox:/media$ ll
total 24
drwxr-xr-x   4 root root    4096 giu 24  2021 ./
drwxr-xr-x  20 root root    4096 ago  2  2021 ../
drwxrwx---   1 root vboxsf 12288 nov  1 10:58 sf_VirtualBox_cartella_condivisa/
drwxr-x---+  4 root root    4096 nov  8 15:24 tommaso/

restarted the VM but the problem remains.

And if I try to access the shared folder form my explorer folder UI I get

authentication is required to access gvfsd daemon

What could I possibly did wrong? How can I fix it?