I have the same problem with the 20s, I had the original 10s when it gave up the ghost and I didn't change anything other than the Sena. I went back and forth with Sena, sent the 2 Sena units back for an exchange (they thought I had bad units) and still can't connect with the Zumo.
The only way I can take a call is to connect the Sena to the phone (iPhone), while I still have the Sena paired to the Zumo for navigation and music. I too wanted to see who was calling, now I have to mount the phone to the handlebar.
[SIGPIC][/SIGPIC]Hojo in SC
Iron Butt Association member 24485