We had an issue on a QNAP QuTS hero NAS joined to Active Directory.
The domain user had Full Control in the folder ACL and Read/Write permission on the shared folder, but the user could only read the files and could not create, modify, or delete anything.
The permissions were actually correct.
The problem was related to time synchronization between the QNAP NAS and the Domain Controller. In Control Panel → General Settings → Time, the NAS was configured to synchronize with our Domain Controller, but Test Connection returned “Failed.”
We reconfigured/reconnected the NAS to the Domain Controller and corrected the time synchronization. After that, Test Connection returned “Success” and the domain user’s write access started working normally without changing the folder permissions.
So, if your AD user shows Full Control/Read-Write but still cannot write to an SMB shared folder, check the NAS date/time, NTP synchronization, and communication with the Domain Controller before troubleshooting the ACLs.
Environment: QNAP TS-h3087XU-RP / QuTS hero h5.2.9 / Active Directory domain.
Eng. Eidi
Eng. Javadi