Herbta, try removing the share from the systems it is not working on and then add it back in. You do not have to delete the data, just open BTSync, click the folder tab, select the folder, click Remove Sync Folder, hit ok. Then click Add a Sync Folder and point back to the same location and add the secret. Also make sure you are running the latest version of the BT Sync client on all nodes. And since you upgraded the OS, if the previous two ideas don't work try uninstall, reboot, install for BTSync.