windows server 2012

You were faced with a situation in which a user X complained that he cant access a network share. You checked both the share and NTFS permissions; they were all fine. You even used the Effective Permission tool and it indicated that this user should have access to this shared folder. You also checked the Group Policies applied to that user and all allowed him access. Would you explain what else might be the reason that prevented the user from accessing the shared folder?