Why does Coros backfill return nothing?

Both behaviours are provider-side limitations on Coros, not Terra.

Both behaviours are provider-side limitations on Coros, not Terra.

• Historical depth is capped. For Coros, Terra can request up to 3 months into the past from the current point in time, or 24 hours prior to the user's authentication, whichever limit is hit first. Older backfill requests return nothing beyond that window.

• Native activities only. Coros only delivers activities recorded on a Coros device through its API. Manually uploaded or third-party activities are excluded.

To pull what is available, request historical data with a start_date inside that window.