Garmin Software Update 23.39 Breaks Heart Rate Sensors on Fenix 8 Watches
A software update for Garmin Fenix 8 and Tactix 8 smartwatches disables optical heart rate sensors and disrupts sleep tracking for some users.
A software update aimed at improving Garmin smartwatches has left some users without heart rate monitoring. According to a report published on Monday by Notebookcheck, owners of Fenix 8 watches complain that after installing software version 23.39, the optical heart rate sensor stopped working. For some, the glitch also disrupts sleep tracking and recovery metrics.
In their complaints, users describe how the sensor lights turned off and heart rate readings disappeared. Since the sensor is used for additional measurements, the impact extends to blood oxygen saturation (SpO2) and nightly heart rate variability (HRV) tracking. Some users also report the disappearance of sleep data and Body Battery statistics, Garmin's energy monitoring metric.
Currently, there is no universal fix. Some watch owners managed to restore sensor functionality by performing a full shutdown for at least 90 seconds and restarting. Others reported that a factory reset resolved the issue. However, for other users, neither extended shutdown nor reinstallation of the software helped.
Similar complaints have emerged among Tactix 8 owners, raising the possibility that the problem is not limited to the Fenix 8. Reports do not indicate that all watches with the update installed are affected.
Garmin has already completed the rollout of version 23.39, which was intended to fix bugs and add features, including voice activation via the phrase "OK Garmin", running workouts, and Garmin Coach improvements. A previous version, 23.31, also triggered complaints regarding software issues—and now some users are dealing with another malfunction.
