I think I found the solution to my problem, since I have already done those things. I did the following on both computers and it works now:
I opened Win Explorer and went to C:\Users\UserName.
Then on the toolbar just above Win Explorer, I clicked on "Share With", then Specific People.
Then I clicked on the dropdown and selected "Everyone", then clicked on ADD, and it added Everyone to the box below.
Then next to Everyone, under Permission Level, I checked Read/Write.
Then I clicked on "Share" at the bottom and closed everything else down.
I hope this will help others with this same problem.