SOLVED - Excel 21 stating "Microsoft has blocked macros from running because the source of this file is untrusted." for a network file

Excel is treating the NAS share as an untrusted “Internet” location, so macros are blocked even though the file has no Unblock checkbox. To allow the macros to run, the location of the NAS must be moved into a trusted zone or trusted location according to how Office evaluates Mark of the Web (MOTW) and zones.

Use one of these supported approaches:

1. Add the NAS share to a trusted zone in Windows

Excel uses Windows Internet security zones to decide whether macros from a network share are blocked. If the share is seen as Internet/Restricted, macros are blocked; if it is Local intranet or Trusted sites, they are allowed.

On the Windows device:

1. Open Control Panel → Internet Options → Security.
2. Select either Trusted sites (recommended) or Local intranet.
3. Click Sites.
4. Add the NAS by FQDN or IP address, for example:
   • \\192.168.0.50 or
   • http://192.168.0.50 (if using HTTP)
5. If adding a UNC or http:// path, clear Require server verification (https:) for all sites in this zone.

After this, the share is no longer treated as Internet/Restricted, so macros in files from that location are not blocked by default.

If managing multiple devices, the same can be done centrally via Group Policy using the Site to Zone Assignment List policy under:

• Windows Components\Internet Explorer\Internet Control Panel\Security Page (Computer or User Configuration).

2. Use a Trusted Location in Office (if allowed)

If the Trust Center currently refuses the path, it is because Excel still considers it a high‑risk network location. After adding the NAS to Trusted sites or Local intranet as above, retry:

1. In Excel, go to File → Options → Trust Center → Trust Center Settings.
2. Select Trusted Locations.
3. Ensure Allow Trusted Locations on my network (not recommended) is checked.
4. Add a specific folder on the NAS, for example Z:\User\Shared.

Files in a Trusted Location are allowed to run macros without being blocked by the Trust Center.

3. Verify the file is not marked as from the Internet

If the file was ever downloaded or emailed and then saved to the NAS, it might carry Mark of the Web (ZoneId=3). In that case, even from a network share, macros are blocked.

On a local copy of the file (for testing):

• Right‑click → Properties → if present, tick Unblock on the General tab. This removes MOTW.
• Alternatively, use the PowerShell Unblock-File cmdlet as described in the documentation to remove the ZoneId.

Once MOTW is removed and the NAS is in a trusted zone, macros in that file will run by default unless blocked by policy.

4. If the share is still treated as Internet

If, after these changes, Excel still blocks macros:

• Confirm the NAS path is actually in Trusted sites or Local intranet by checking Control Panel → Internet Options → Security and reviewing the site list.
• Ensure the mapped drive Z: is pointing to the same UNC/host that was added to the zone (for example, if the mapping uses \\192.168.0.50\User, that exact host/IP must be in the zone list).

Once the NAS share is in Trusted sites or Local intranet, and the file is not marked with ZoneId=3/4, Excel will stop showing “Microsoft has blocked macros from running because the source of this file is untrusted” for that workbook.

References:

• Macros from the internet are blocked by default in Office
• Block or unblock external content in Office documents
• Excel is blocking untrusted XLL add-ins by default