JMMONTER087
I read through the posts again and I didn't see mention of a Master Reset for the 910XT. I try to only suggest those as a last resort. Please see the information in the FAQ:
How do I master reset my Forerunner 910XT?
Curt
JMMMONTER087
I am sorry for the troubles. At this point you should be working exclusively with Garmin Express on the Mac. Have you gone through the suggestions in the FAQ: What troubleshooting options can I try when my ANT enabled fitness device will not upload data?
Curt