Are you trying to add a new activity type to the list of accepted activity types? If so, this is not something that you can do. The activity types supported by Garmin Connect are almost hard-wired into their system. Users have been begging for additional (or customizable) activity types, but it hasn't happened.
Why is there not enough sports types in Garmin connect??
It's ridiculous the amount of "other" i have to put on my training plans and the amount of time I have to put the nearest thing to it even though it isn't correct. why have triathlon transitions but not triathlon?? Garmin you need more sports and activities on Garmin connect!!!!! There is no: Triathlon, Yoga, circuit training, Netball, Basketball, Rugby, Volleyball. These are my main sports/activities.