On Fri, 18 May 2018 09:33:06 -0400, Pat wrote:

This was my original post from May 9th:

I have two nearly identical PCs both running Windows 10. Both were
updated from 1709 to 1803 about a week ago. All went well with the
update except neither machine was able to share files with the other.
After googling the problem, I saw many were having the same issue.
I found people who had solved the issue by starting the "Function
Discovery Resource Publication" service. That solved part of my
problem. The two PCs can now see each other, but they still can't
access any files on each other. I tried installing the SMB feature in
Windows, but nothing changed. (I didn't expect it to since it was
proposed as a way to talk to Win 7 machines.) I stumbled across using
"RUN" to access files on the other machine. Typing "\\PC-B\MyDir"
into the run window on PC-A works. I get the directory and can access
the files. If I leave that window open, I can then use file explorer
to access the files on PC-B. However, if I try File Explorer without
having first used RUN, then I get error 0x80070035 (Network Path Not
Found). I could almost live with that except PC-B never sees the
files on PC-A no matter what I try. I always get the 0x80070035 error
regardless of whether I am using RUN or file explorer. My intent is
that PC-A and PC-B be configured identically so I can't see why typing
"\\PC-x\MyDir" works in one direction but not the other. The only
intentional difference between PC-A's and PC-B's configuration is IIS
is running on PC-A but not PC-B. But, I don't see that as having
anything to do with file sharing.

UPDATE:
I tried many different suggestions I received from some of you but had
no luck. Yesterday, I accidentally stumbled into a solution. I
noticed PC-B was set to DHCP instead of the static IP it had been
assigned years ago. I set it back to static thinking it had nothing
to do with my sharing issue. However, instead of PC-A being able to
access PC-B's files (but not the other way around), now neither PC
could access the other's file. I then set both PCs to use DHCP (but
still keeping the same IP address via the router's "reserve"
function). All is now back to normal.

So, I fixed it but still don't understand it. What does DHCP vs
static have to do with file sharing (but only after installing 1803)?

Much of it has to do with the specific IP addresses involved, their
respective netmasks, and the nature of how you were trying to access one
PC from the other.