Garmin Fenix 8 users report problems and missing features following update 23.39

Garmin’s Fenix 8 has run into another software problem, with some owners reporting that firmware version 23.39 disables its optical heart-rate sensor. Affected users describe the sensor's LEDs going dark and readings vanishing, which also disables Pulse Ox and overnight HRV. Some report missing sleep and Body Battery data too.

There is no universal fix so far. Some Fenix 8 owners have restored the sensor by powering the watch down completely for at least 90 seconds before restarting it, while others have reported success with a factory reset. Reinstalling the firmware or performing an extended shutdown has not worked for everyone. Similar reports have also emerged from Tactix 8 users, suggesting the problem may extend beyond the Fenix 8.

The timing is awkward because 23.39 was intended to address bugs and add features, including the "OK Garmin" voice wake phrase, a running workout and Garmin Coach improvements. Garmin has completed the rollout, and reports do not indicate that every watch is affected. However, complaints also appeared with earlier software 23.31, making this another messy episode for Garmin’s flagship firmware updates.