Hi giiancarlo, I hope your doing well despite the problem you are experiencing now and I'm sorry for that. For that let me try to assist you.
If you already have set your sharing of folder and the right privileges, we might need to look into other services of Windows. Please take a look at the link below, and check if you haven't missed any of the solutions provided.
https://learn.microsoft.com/en-us/troubleshoot/...
I hope this helps. Please let me know if I didn't address your problem. Don't hesitate to ask for further assistance.
Regards,
Arnel