Android 4.4 - Moto X.
After I installed the Pebble Time app and updated my Classic Pebble firmware, MapMyRun quit working. The splits/time display wouldn't show on the watch, and the link indicator in MapMyRun was grayed out.
Here's how I fixed it: Leaving the new Pebble Time app installed and connected to the watch, I reinstalled the old original Pebble app on the phone, and went through the first step (where you select the type of Pebble) but didn't log in. Now MapMyRun sees the watch and the display works normally. Management of the watch (firmware upgrades, installing other apps, and faces etc) is through the new Pebble Time app like it should be.
I believe there must be a linked library or API that wasn't brought across to the new Pebble Time app. The only 'glitch' I get with this arrangement is sometimes I get "Pebble is connected" from the Time app, but "Pebble is disconnected" from the original app. Small price to pay, I guess.