I have every folder set to share with everybody and full permissions for that.
One computer (Call it A) can be read like an open book by one of the other Win10 computers (call it B). The laptop gets this error.
If I try to read a folder on the B computer from the A computer is has this error.
On every folder except one which reads and writes just fine. The rest have the second error above. And clicking that link is useless. Here is the link:
https://support.microsoft.com/en-us/products/windows?os=windows-10
The Homegroup is all set to the same name. There should not be a password anywhere.
I will keep digging on the help sites. There HAS to be a simple way to do this. If not, someone can make a fortune in writing a program that allows Win 10 sharing with no jumping through hoops.