Win10 can't connect to Win8.1 but Win8.1 can connect to Win10

You are welcome. You gave it a valiant effort & did discover some workarounds along the way. Good going though they don't last. The ball is in MSFT's court now. Good luck & keep us informed. Careful on those stairs.

(Hmm, so it isn't strictly a Win 8.1 problem. OK.)

For the record, here is my key...

It doesn't have AllowInsecureGuestAuth at all which normally means it is set to 0 (off).

One additional note... while this started out trying to access a win8.1 computer from the win10Pro computer in question, when other win10 computers, both home and pro, were added to the lan, they could not be accessed either, but they could access the problem computer's shares.

It would be interesting to know if others who have posted suggestions in this thread have the parameter AllowInsecureGuestAuth in the registry key

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters and if they have the parameter, what is it set to?

From my reading of this thread and others that I posted to over the past year and a half plus, I have not observed anyone who has actually had or seen the same problem that I (and others who have posted elsewhere) have experienced.

All of the suggestions posted in this thread and others have merit and value related to similar general file sharing problems, but, none of the solutions posted addressed this specific problem... i.e. the computer is unable to connect to other computers on the lan, but all other computers on the lan were able to connect to this computer with no access and sharing problems.

At this point, I am firmly convinced that if the above parameter is set to "0" that none of the file sharing settings or user rights privileges posted here and elsewhere have any bearing on this lockout.

While I was unable to research or address this problem for over a year, I will note that I have extensive lan experience and have been sharing and transferring files since the 80's before windows and before it was even a microsoft option.

Looking at the design and behavior of this parameter setting, it is clearly designed to restrict the computer and user from connecting to any lan file share... while it states "open share" that was not the case since turning password protection on and off on the inaccessible computer had no effect on the restriction.  In fact, the file explorer failure message states that the computer "does not exist" rather than any mention of any restriction... a good way to get a casual user to "go away"

One final thought... most files that I share and need access to to and from other computers are kept in the "user\public" tree.  THAT could also relate to this restriction in addition to the sharing settings since the os might be making a decision on the "public" location.

Thanks again to everyone who posted, but, I sincerely hope that this specific case will be looked and and saved as yet another microsoft "gotcha" so that those who run into it will be able to address it.

Now, we get to deal with apparent major os changes from ms that have "restrict" as a major design category  <sigh>

Beverly Howard

[(former)MS MVP]

Here is a recent thread discussing the file sharing problem...

https://answers.microsoft.com/en-us/windows/forum/all/is-it-safe-to-turn-off-password-protection-on-a/16ddb7e6-ff29-48be-b2a1-154eb2ba4394?page=1

Is it safe to turn off password protection on a home network? All PC's do have internet access as well.

AlexMegan announced a solution on page 2 of that thread reminiscent of what you found on page 2 of this one. He switched one of his computers from an Admin account to a Standard account to cure his file sharing/credentials problem. I don't know whether he thinks it will be permanent or not, but I think you discovered it will not. I don't know what versions of Windows are on his computers.

You may as well pop into there in case a permanent solution is found. And I think you've got a lot you can contribute.

You are welcome. Sorry once again I couldn't solve it. 21H2 is coming soon to update your Win 10 machines, but somehow I came to think it's the Win 8.1 computer at fault. Maybe it isn't doing its FDResPub.

Good luck, & keep us informed.