Got a few questions. You're using a Galaxy Note 4 with the latest OS, but you didn't mention which carrier. Do you have navigation?
If you haven't already, start by checking here:
http://www.infinitiusa.com/bluetooth/search
Nissan/Infiniti limits the number of paired phones to five different phones. I'll assume that would also mean five different bluetooth devices.
FAQ's:
Q: How many phones can I pair?
A: The system supports up to five different phones. However, only one phone can be used at a time.
This may explain why the other devices are greyed out. The system allows only one device at a time. And I'd hazard a guess that it's optimized to work with cell phones, but may not play nice with other devices, especially a newer gadget like the smartwatch.