Garmin Fenix 8 owners are facing a fresh software headache after the latest firmware update, with some users reporting that version 23.39 has caused the watch’s optical heart-rate sensor to stop working.
According to affected owners, the issue appears after installing the update, leaving the heart-rate sensor LEDs inactive and removing live heart-rate readings from the watch. Because Garmin’s health tracking features rely heavily on that sensor, the problem can also affect Pulse Ox measurements, overnight HRV tracking, sleep data, and Body Battery readings.
For a smartwatch built around advanced fitness, health, and recovery metrics, losing heart-rate tracking can seriously reduce the usefulness of the device. The Fenix 8 is positioned as one of Garmin’s premium multisport watches, so reports of missing core health data have understandably frustrated users who depend on the watch for daily training and recovery insights.
At the moment, there does not appear to be one guaranteed fix. Some users say they managed to restore the optical heart-rate sensor by fully powering off the Garmin Fenix 8 and leaving it shut down for at least 90 seconds before turning it back on. Others have reported that a factory reset brought the sensor back.
However, these solutions are not working for everyone. Some owners say reinstalling the firmware or leaving the watch powered off for a longer period has made no difference. That suggests the bug may not behave the same way across all affected devices.
The issue may also extend beyond the Fenix 8. Similar complaints have appeared from Garmin Tactix 8 users, indicating that the problem could be tied to shared software components across Garmin’s latest premium watch lineup.
Firmware version 23.39 was meant to improve the user experience rather than create new problems. The update included bug fixes and new features, such as the “OK Garmin” voice wake phrase, running workout improvements, and Garmin Coach updates. Garmin has completed the rollout, but current user reports suggest not every Fenix 8 is affected.
Adding to the frustration, some users claim related problems were already present in earlier firmware version 23.31. That makes the latest situation another difficult moment for Garmin’s flagship smartwatch software, especially for owners who expect reliable health tracking from a high-end wearable.
For now, affected Garmin Fenix 8 users may want to try a full shutdown and restart first, followed by a factory reset if necessary. Before resetting, users should make sure their data is synced to avoid losing important activity or health records. If the heart-rate sensor still does not return, waiting for Garmin to release another firmware fix may be the only option.
