I have a late 2013 MacBook Pro running OS Big Sur (just upgraded from Mojave). This is connected via a Thunderbolt cable to a 2019 iMac running Monterey (also just upgraded from Mojave). From the MacBook I was able, before the upgrades, to access the folder structure on the iMac. i did this by clicking Network in the finder window sidebar, then navigating to the folder that I wanted to see. Now, I can navigate through the volume iMac, Users, [my name], so that I can see the Documents folder in the finder window, but when I try to view the Documents folder I just get an empty window, and cannot see any of the contents of the folder.
I need to be able to see the Documents folder on the iMac, across my network, so that I can synchronise the two devices, which I do using the Chronosync application.