File & printer sharing stopped working - cannot access [\\NAME]

I recently bought a pair of new laptops with Windows 10. When I set up file & printer sharing between them, it worked fine. A couple of days later, the sharing stopped working (possibly following a Windows or driver update), although I have not changed any network or security settings, and both machines can still see each other in File Explorer > Network, but when I try to access one from the other, I get an error message: “Network error. Windows cannot access \\[NAME]. You do not have permission to access [NAME]."

I tried Settings > Network & Internet > Network Reset, but it did not help.

I also have an older pair of laptops with Windows 7 on which I have file & printer sharing set up in exactly the same way, and it still works fine on them, and when I compared the network and security settings on the old and new laptops, they were all the same, except for one difference: in C:\ Properties > Security, the permissions for the SYSTEM, Administrators, and Users groups were all the same; however, on the new laptops, the permissions for the Authenticated Users group were all blank, whereas on the old laptops, these were ticked: Modify, Read & execute, List folder contents, Read, Write.

When I ticked these and clicked on "Apply" on the new laptops, I got a warning message ("You are about to change permissions on the root directory of the startup disk. This can reduce the security of your computer and cause users to have problems accessing files. Do you want to continue?"), and when I clicked on "Continue", I got a series of error messages (“An error occurred while applying security information to: ...”) for the following folders:
- C:\hiberfil.sys ["The process cannot access the file because it is being used by another process."]
- C:\pagefile.sys ["The process cannot access the file because it is being used by another process."]
- C:\Program Files ["Failed to enumerate objects in the container. Access is denied."]
- C:\Program Files (x86) ["Failed to enumerate objects in the container. Access is denied."]
- C:\Recovery ["Failed to enumerate objects in the container. Access is denied."]
- C:\swapfile.sys ["The process cannot access the file because it is being used by another process."]
- C:\Windows ["Failed to enumerate objects in the container. Access is denied."]

I then noted that the owner of C:\ is “TrustedInstaller”, and I gather that I may need to change the ownership in order to change the permissions? I also gather that there are a couple of ways to do this, but I am wondering what is the best way and whether this could cause other problems?

(It is unclear whether the blank C:\ permissions for the Authenticated Users group are the reason behind the file & printer sharing issue, but I want to confirm the permissions before investigating further.)

Thanks for your reply. Are you saying that in your case:
- the sharing was working fine and then stopped for no apparent reason (no settings changed),
- the sharing started working again after you just restarted both machines a couple of times, and
- the permissions for the Authenticated Users group on C:\ were/are blank (so this may not be relevant to the sharing issue)?

OK thanks. I tried restarting both of my machines a couple of times, but it did not help. When I try to access one from the other, I keep getting an error message: “Network error. Windows cannot access \\[NAME]. You do not have permission to access [NAME]."

Both machines were recently updated with "Feature update, version 1909", and I am now wondering whether this issue might be something to do with the new version.

Have you setup shares and set permission on the share to everyone have you then set NTFS permission confirm? Any major update it is effect a new version of windows and new network

Yes, I tried removing the file & printer sharing, restarting, re-adding the file & printer sharing, and restarting again, but it is still the same: in File Explorer, each machine can see the other, but when I click on it, I get "Network error. Windows cannot access \\[NAME]. You do not have permission to access [NAME]."

However, I have found that if I make a desktop shortcut to the Public folder on the other machine (i.e., "\\[NAME]\Users\Public"), then that works! (Printer sharing still does not work though.) I am starting to suspect even more that the issue is not to do with security permissions (which I have not changed) but some other change (bug?) in the networking functionality in the recent "Feature update, version 1909".