I'm having the same issue. I set up a folder on one Mac (running macOS Sierra - latest version), pasted the link code into the Sync app on the other and it sent an approval request. I approved it on the first Mac but it claims no peers online and the other Mac still says 'Pending approval'. How do I fix this?
I have a number of hidden (as in they start with a dot) folders can't can't see a way to manually add them. Sync only allows me to choose them using the default file picker. Is there a way to manually add hidden folders to be synced. I am on macOS Sierra.