Hello Thomas Chantziaras, thank you for posting in the Microsoft Q&A community.
Because this is isolated to a single user and machine, and the LastUploadTime as well as the server copy of NTUSER.DAT have not updated since February 14, 2026, the issue is likely localized rather than a domain-wide configuration problem. Typically, this behavior occurs due to a few common root causes. First, a third-party application or background process (like an antivirus scan or backup agent) might be holding a file lock on NTUSER.DAT during the logoff process, which completely blocks synchronization. Second, there may have been permission or ownership changes on the Windows Server file share, causing the user to lose the required rights over their own profile folder. Additionally, the local cached profile on the workstation might be stuck in a corrupted state that Windows is internally treating as a "Mandatory" profile, intentionally discarding uploads. Finally, a localized Group Policy or registry setting could be interfering with the upload process.
To resolve this, we can start with the most common approach, which involves ensuring permissions are correctly applied and clearing the local cache to force a clean sync. First, on your Windows Server 2019 file share, right-click the affected user's roaming profile folder, go to Properties, select the Security tab, and click Advanced. Verify that the user account is set as the Owner of the folder and has Full Control permissions over this folder, subfolders, and files.
Next, on the affected Windows 11 workstation, log in using a local or domain administrator account (do not log in as the affected user). Press Win + R, type sysdm.cpl, and press Enter. Navigate to the Advanced tab and click Settings under the User Profiles section. Select the affected user's profile and click Delete to remove the local cached copy. After this, open the Registry Editor and navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList. Look through the subkeys to find the SID associated with the affected user and delete that specific key if it still exists. Have the user log back in to pull a fresh copy of the profile from the server, make a small change like creating a text file on the desktop, and log off to see if the synchronization successfully completes.
If this does not fix the issue, you can use another workaround by entirely recreating the profile on the server side. Rename the user's current roaming profile folder on the file server (for example, renaming it to username.V6_Backup). When the user next logs into the Windows 11 machine, a brand new local profile will be created. Upon logoff, Windows will build a fresh, uncorrupted profile folder on the server. You can then manually copy essential personal data (like Documents or Favorites) from the backup to the new profile, ensuring you do not copy the old NTUSER.DAT or hidden AppData folders, which likely contain the root corruption.
Official Microsoft documentation for your reference: Deploy roaming user profiles | Microsoft Learn Troubleshoot user profiles with events - Windows Server | Microsoft Learn