Problem Description
I’m trying to access an external hard drive connected to my A1 WLAN Box DX3301-T0 (Zyxel) modem via SMB from my Windows laptop. The goal is to add the files to my Plex Media Server, but I can’t get Windows to connect to the share.  

Setup:

• Modem: A1 WLAN Box DX3301-T0 (Zyxel)  
• Mesh System: TP-Link Deco HX220 (modem’s Wi-Fi is off, mesh handles wireless)  
• USB Drive: Connected to modem’s USB port, recognized in GUI  
• Share Settings:  
  • Share Path: `/mnt/usb2_sda/Series`
  • Share Name: `Series`  
  • File Sharing Services: Enabled  
  • Default Gateway: `10.0.0.138`  

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Attempted Solutions (All Failed)

1. SMB Access via File Explorer
   - Tried `\\10.0.0.138\Series` → Error 0x80004005 (Unspecified Error).  
   - Tried `http://10.0.0.138/mnt/usb2_sda/Series` → Shows unstyled GUI page (no file listing).  
   - Modem appears in Network Explorer (DX3301-T0), but clicking it opens the web GUI.  

2. Credentials Tested
   - Used modem’s admin credentials (same as GUI login) → Access Denied.  
   - Tried `guest` (blank password) → No success.  
   - No separate SMB/FTP credentials available in GUI.  

3. SMB Protocol Adjustments
   - Enabled SMB1 (temporarily) → No change.  
   - Forced Guest Access via Registry (`AllowInsecureGuestAuth=1`) → Still fails.  
   - Checked SMB connections via PowerShell (`Get-SmbConnection`) → No active connections.  

4. Network Drive Mapping
   - Attempted to map `\\10.0.0.138\Series` → Same error.  

5. Modem GUI Options Checked
   - No FTP or SMB version settings available.  
   - No guest access toggle for the USB share.  
   - Reformatted USB drive to FAT32 → No improvement

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Additional Observations

• The modem’s "File Sharing" feature seems limited—no advanced SMB/FTP controls.  
• No firmware updates available from A1/Zyxel.

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Request for Help

• Has anyone successfully accessed a USB share on the A1 DX3301-T0 modem?  
• Are there hidden SMB settings or alternative methods (WebDAV, NFS)?  
• Could the TP-Link HX220 mesh be interfering? (Modem handles the USB share, not the mesh.)  
• Any registry hacks or third-party tools that might help?

Thanks in advance for any suggestions!