Hi, unfortunately this is a well known problem in gear fit manager (I'm currently using the 1.98.1127 version).
Finally this morning I discover a workaround solution to temporarely fix the problem.
So I suggest you to follow this procedure:
1) Set an alarm on your mobile phone (for example 5 minutes from current time )
2) Verify that the sound in your mobile phone is enabled (not just vibration).
3) when alarm raise DO NOT STOP using the gear fit but use the mobile phone itself.
that's all.
Now try to find your device using the gear fit.
For me it's works well.
Let me known.
cheers
DNAF