For months during the Technical and Insider Preview stages of the Win10 version track, I noticed that some of my PCs would switch from Private to Public network status following sleep (tablets, mostly — both Surface and Dell Venue Pro 11 proved occasionally susceptible). The easy fix on my home network which lacks an Active Directory server is to launch the HomeGroup applet in Control Panel: this immediately informs me that the network is Public and must be reset to Private before HomeGroup access is available. On an AD network, machines that fall prey to this gotcha must instead be reset from Public to Domain, as explained in this excellent tutorial on the TenForums.com website “How to Set Network Location to be Public or Private in Windows 10.”
Once you get into the properties for your adapter (Ethernet or Wi-Fi in most cases), you should turn this setting On.
For those to whom the HomeGroup method is not applicable, the quickest method to regain access to proper network status is to dig into the Network and Internet silo in the Settings app in Windows 10. Once into that silo, pick Ethernet for wired PCs and Wi-Fi for wireless ones, then make sure the setting for “Find devices and content” is turned on, as shown for Ethernet in the preceding screen cap. This will automatically confer the proper network status for those who have administrative access to their PCs. Those who lack such access will have to get some help from their Help Desk or local administrator, to restore their PCs to normal (and expected) functionality.
Here’s hoping that MS will be able to finally find and fix this occasional glitch in some forthcoming update to Windows 10, preferably sooner rather than later. In the interim, the preceding approach will help users get back on the network (and back to work) with minimal muss and fuss. Please consult the afore-linked TenForums tutorial for alternate fixes based on registry hacks, local security policy, or PowerShell (all of which work for both HomeGroup and Domain situations with varying degrees of success; Domain Admins will also want to investigate edits to domain security policy as well).