MacMini 2011+ Sierra upgrade = 'not supported' bluetooth...

Hi -

I've upgraded my MacMini (Mid-2011 Server) to macOS Sierra 10.12 and now I cannot pair it with my iPhone 6S+ (iOS 10.0.2). Both devices see each other via bluetooth, but when I go to pair the devices I get a message on my iPhone "Connection Unsuccessful - MacMini is not supported" -- the only option to choose being "Forget Device". These two devices worked just fine together before Sierra. Any fixes for this? Don't say 'toggle bluetooth on/off' or 'restart devices' -- I've done all of that. Apple products user for 20 years, so I'm pretty familiar with the standard things to try.