SMB: Operation not permitted

Hi,

for some reason I cannot connect to SMB shares I have from a windows server 2016, I can access these shares fine from any other PC and kodi can access smb shares on my windows 7 host but even though I entered username and password for the share, event log on the server shows that kodi still tries logging in with a null user id.
enabling guest account (which is not enabled on the windows 7 host where it does work) does not work either…
any clue why this could be happening and how to fix it?