EDIT:
Sorry, this was just a mistake on my part. I missed the fact that the UX element for adding gear has always been in one place (near the top), while the UX element that actually shows your gear is on the bottom-right hand corner (and it disappears when you remove gear).
While I don't like this UX (especially since the 2nd UX element literally says "Change Gear" and it disappears when you remove gear), it's totally not a bug.
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OP: BUG: Cannot add gear to activity unless it already has gear
Looks like there's a new bug in Garmin Connect Web where you can't add gear to an activity that doesn't already have gear. The button/link for managing gear ("Change Gear") is completely missing in this case.
As noted in another thread, this is obvious if you import an activity manually.
This may have been missed because most people have default gear for running or cycling that automatically gets added to the activity.
Recreation procedure:
- Navigate to existing activity in GC web
- Remove existing gear
- Observe that the "Change Gear" link for editing gear disappears and there's no way to bring it back
OR
- Create an activity that doesn't have default gear (e.g. Strength.)