Update 8/1/2015: From the comments, this problem seems to exist in the released, post 7/29/2015 Windows 10 as well (we don’t call it the release-to-manufacturer, or RTM, version any longer).
Update 8/3/2015: I conducted additional testing after some comments brought up other issues, such as some NAS devices not having an SMB setting (see below), and I ran into all sorts of problems. I deleted my credentials for the NAS device in Control Panel > Credential Manager > Windows Credentials, and then reset the SMB settings as indicated in this post. I couldn’t connect, which surprised me. I tried all sorts of combinations, including manually creating a credential as one commenter suggested, and still couldn’t connect.
Even more strangely, I had multiple shares mapped to folders on the same NAS device, and one could connect (with no credential listed in Credential Manager) while the others couldn’t. Bizarre.
Finally, I rebooted my machine, changed the SMB settings in the NAS device again, and then finally reconnected successfully. And so, while I recognize that this fix doesn’t work for everyone, it still seems like the best fix for now. Microsoft has some work to do in cleaning up how Windows 10 connects to such devices, because I can confirm it’s something of a mess right now.
I’ll be reporting on Windows 10 as I have a chance to work with it on my various machines, but I wanted to report quickly on a very specific problem that I’ve experienced. Specifically, I was unable to connect to my Western Digital MyCloud Mirror network-attached storage (NAS) device. On any of my Windows 10 installs, attempting to connect to the NAS returned a permissions error before I was given a chance to authenticate (and I’d provide a screenshot of that error, but I can’t duplicate it after applying this fix).
A bit of research unearthed the culprit, and I’m not sure if this is a general NAS problem or something specific to Western Digital devices. And, strangely, once I applied the fix and then reverted back to the original setting, the problem never came back. So, I’m not sure if it’s a Windows 10 problem, a WD NAS problem, or just how the two work together in establishing connections.
In any event, the fix was quite simple: just go into the NAS network settings on the NAS device and turn the SMB protocol to SMB1 (as opposed to SMB2 or SMB3). Once I made this change, I could connect. And, setting SMB back to SMB2 or SMB3 doesn’t cause any of my Windows 10 machines to stop working. I applied the fix on my desktop machine and reverted it, and my Surface Pro 3 was able to connect no matter the setting.
So, there you have it. I’m not sure how helpful that is or what about Windows 10 caused the issue, but this fix seems to be permanent. Let me know if it helped you out.
Update: I had a request for more specific instructions on how to access the correct settings, and here’s where to go on my MyCloud Mirror device. Other MyCloud devices might have different interfaces, and of course other NAS devices are certain to be different, but in general the SMB settings should be wherever Windows networking is configured.
On the MyCloud Mirror, you first go to the Settings option in the toolbar running across the screen, then to Network settings:
Then, scroll down the page to the Windows Services settings, and change Max SMB Protocol to SMB1 (mine is set at SMB3, because as I noted above my machines will now connect at this setting):