I am trying a simple folder pair, the "test" down the bottom works. I have tried default checkbox settings and all ticked. I have tried in single and dual pane.
When I navigate to the tested folder nothing happens. I googled and searched youtube on folder pairs but didn't find anything.
This is kind of a simplistic answer, but I think I know what you may be looking for.
To activate the paired folder in the other file display you can use Folder -> Paired Folder.
What I use is, be it the best answer or not, is this script by @lxp that will auto open them.
Thanks for the script suggestion, now it does exactly what I expected it to do rather than having no obvious effect (and the documentation not really saying what to expect).
I don't understand the folder suggestion as that doesn't seem to be in the folder context menu or anywhere else I could locate.
Try the toolbar below. If one member of a pair is open a button will appear indicating the existence of a pair. If you click on this button, the other pair member will open. An option to turn on Nav Lock is also included.