Hello Martí Carrasco Guitart,
Thanks for posting here.
As per your statement, the whole set is secured and connected through the VPN deployed with WireGuard, while it`s available on your mobile and Mac but not Windows. Free feel to correct if my understanding might be incorrected.
Due to the NAS may be using CIFS / SMB 1.0 and is disabled by default in Windows 10 for it is less secure than newer versions of SMB.
You can try the following steps to see if it helps:
Open Control Panel, click Programs and then find "Turn Windows features on or off" and click it.
As shown in the picture below, if your SMB1.0/CIFS file share support is not enabled yet, you can try checking it to enable it.
Then, restart your computer, and if possible, try to connect / map to the NAS drive again.
I hope this can help you.
If you have already tried this, please reply, and let us know and we would be happy to provide some different suggestions!
Best Regards,
Shujun
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