Heart Rate Data and External Coros Arm Band Monitor

i am very happy with the performance of the optical hr of the watch, i have chest strap but normally i use it for intervals, for easy runs the watch is very precise, has a little more latency that the chest strap, i compared some trainings wearing both, and the data of the ohr of the watch is nearly identical of the chest strap, if your unit is unstable, try to delete all data and reset to defaults, the firmware im using 19.18, not very happy with it, because some flaws in the barometer sensor and something more, but for running is fine

If you are happy with a device that works for some of your workouts most of the time then great. That's not me. I don't want to have to complete an IT project just to get an accurate heart rate. I don't want to have to know what version of firmware I'm running. I just want to push a button and go for a run.

For me right now that is using a heart rate strap. I get a little over a year out of each one and then they fail. The recent problem was a new glitch and threw me for a loop.

I've never had luck with the barometer. My old forerunner 920xt also was unreliable for elevation. I just correct using Strava if I'm interested. The oxygen sensor is another piece of useless stuff. If your blood oxygen is low you need to go to the ER. The variation seen on the watch is mostly measurement error. Completely useless in training. 

I love the new Garmin connect. I wish Garmin would focus on equipment and software reliability. I can do without a lot of the fluff.

I followed this procedure this morning for the monitor ( although when I looked at COROS firmware, it said I had the latest version ) . I id the reboot on the armband, reconnected the monitor to the Garmin 255, no change. When I hit run on the activity, the message appears that the COROS monitor is connected, but still no heart rate data flows to the watch. ... Mayve I need to be in COROS Beta program to get a more current firmware

update ?

Did you remove the sensor from your Garmin, and sync it again?

I'm not in a beta test, the firmware version for the Coros HRM is V1.20.0, my Garmin 965 has the software version 20.23.

I run today and it's working fine!

I followed your procedure exactly, removing the Coros HRM from the Garmin 255 device, doing the reset ( 5 x shut down , flashing lights + green ).

I then did the pairing with the Garmin 255, it shows as connected when I start a run , ride , or walk, but no heart rate data goes to the watch.

Firmware version for Coros HRM is V1.20.0 ., software version on the 255 is also 20.23. Thiis now more than curious, it is frustrating. 

Exactly the same for me.

It is very frustrating!!!

I have the same problem since version 20.21 and 20.23 on my 965. The only workaround that is working for me is restarting the watch before each workout. I hope this get fixed soon.