I also sync to a Samsung device, and I was also having connection problems before. Although I still get the red exclamation point on folders that exist, at least MusicBee syncs with my phone.
Here's 2 things to try:
1. When you first plugged your phone into your pc, there should've been a pop up. Did you "Allow access to computer"?
2. When you're plugged in, unlock your phone, pull down to see the notification bar, look for Android System > USB for file transfer. Click on this and make sure that Use USB For is set to Transferring Files.