Why have my Fitbit heart rate fields gone null?

Fitbit heart-rate summary fields are computed from the heart-rate samples the provider sends, so disabling the samples scope in your dashboard also empties the…

Fitbit heart-rate summary fields are computed from the heart-rate samples the provider sends, so disabling the samples scope in your dashboard also empties the summaries. Re-enable the samples scope to restore heart-rate data.

Separately, the status codes in payload history are your endpoint's responses, not Terra's. A 500 there means your server errored on receipt, not that Terra failed to deliver.