This video showed a setting I had not previously changed (though everything else was as shown already) however windows 11 still can't open folders on my networked windows 10 laptop.
It can see it the other computer listed OK and I can also access a portable drive attached to router USB.
What's really annoying is that the windows 10 laptop and a windows 10 desktop can access shared folders the new windows 11 laptop just fine. But try the other way ad Windows11 implies I can't spell the computer name - that it clearly shows is visible on the network.
It's also annoying it invites you to diagnose the problem only to immediately announce it can't find a problem.
It really shouldn't be necessary to fiddle about with obscure hidden settings at all, though it has sometimes been a bit confusing it has always previously been relatively easy to just click the appropriate settings in network and sharing and your shared folders and files are just there.