Thanks for the feedback. The next time the problem happens, I will try all your recommendations. Yes, the documentation you referenced is process I’ve been following. I have done your first recommendation, restoring to factory settings many time, which often does temporarily clear the problem, though later the problem returns. I’ve started to wonder if changing the factory Bluetooth Name and PIN (which I generally have done) causes the pairing to be more unstable, because right after doing a factory reset, it seems easier to pair. Regarding OS X 10.10.4, I’ve been through various OS versions, all with the same problem.
I’ve noticed a lot general weirdness with the device – for example, sometimes it just doesn’t appear in the bluetooth control panel, and I’ll need to reboot the H9 (often more than once) to get it to appear. Or when it does appear and I select “Option” to enter the PIN, it fails to pair despite using the right PIN. And one odd thing is it will sometimes appear in the control panel with it’s factory name, then later revert to the configured name (and this is after using the configured name for several days across several reboots). I don’t know if any of this is an indication of a hardware problem.
Last night it was more challenging that usual to get it paired, and required me rebooting my computer and rebooting the H9 several times; I finally got it to pair, and today the connection still is working. The next time it happens again, I’ll be more systematic with my troubleshooting and will record all the steps taken and the results.