I have two Macbook pro retina's:
- MbPro 15" retina late 2015 El Capitan
- MbPro 15" retina mid 2012 El Capitan
The first one is able to pair with the Magic Trackpad
(not the "2" - instead the older version).
But the 2012 one has the following behavior:
- initially detects the trackpad -including showing the serial #
- but then cannot complete the pairing - and I'm back to square one.
The initial detection of the trackpad happened several times.
But usually I do not even get that far: the trackpad is simply not detected.
There is obviously no problem with signal or batteries (new): the trackpad works all day on the other MBPro.
What should I look for as potential culprits and fixes?