Garmin Fenix 8 Update 23.40 Restores Wrist Heart Rate

Garmin has begun rolling out software version 23.40 for the Fenix 8, fixing a failure that could leave its optical wrist heart-rate sensor completely inactive after version 23.39. According to Gadgets & Wearables, the update has reached 20% of users so far, so many affected owners may still be waiting. This is a proper corrective release, not a new-feature drop.

The issue went well beyond a few dodgy beats per minute. The Fenix 8’s green and red sensor lights could switch off entirely, removing wrist heart rate during activities. Since this is a PPG sensor that reads changes in blood volume with light, its failure also took out data dependent on that optical system: overnight HRV, Pulse Ox, sleep information and Body Battery. For a multisport watch, that is a serious loss of its daily-training value.

Before 23.40, recovery sounded frustratingly random. Gadgets & Wearables reports that some owners got the sensor back by powering the watch off for more than 90 seconds; others tried a factory reset or firmware reinstall. Neither route was dependable, and Garmin support reportedly suggested replacement could be necessary if a reinstall failed. The new firmware strongly points to software as the root cause, so installing it should come before assuming the watch hardware has died. It also lands after version 22.44 addressed display complaints, adding to a rough run of Fenix software fixes. That is awkward timing alongside Garmin’s current premium push, including the [MARQ Gen 3 launch](/en/articles/garmin-marq-gen-3-launches-as-polar-files-h12-2026-10-16).

What is missing? Detail and reach. Garmin has not explained why version 23.39 could disable the sensor, while 23.40 is only available to part of the user base at present. The changelog also lists unspecified minor fixes. It does fix a crash when enabling active heart-rate broadcasting through Garmin Connect Mobile and stops notifications making noise in silent mode, but there are no new training tools here.

Verdict: Fenix 8 owners affected by the blackout should install 23.40 as soon as it appears. It restores a core function, but Garmin needs this rollout to reach everyone quickly and stay fixed.