I use bonjour for syncing between my Mac and iPhone. I had issues initially when setting up the database. It was not showing up anything. How to sync between devonthink pro and go post helped me.
Enable bonjour server on the Mac and connect the phone. If it’s not connecting with Wi-Fi, try cable. Sometimes sync does not happen and to manually sync the phone I do Sync > Locations > Local Network. Sometimes it syncs when on this screen. Or tap refresh.