Not all BLE Devices found by scanning

Thanks for your help, with the above documentation I found the 'bleno' library and used it to further debug the capabilities of our sensors in combination with the Watch.

Now I can fairly certainly say that the issue is with randomized Bluetooth Low Energy addresses.
After updating the sensor firmware to disable the randomized address it showed up in the scanner right away.

This fix is okay to use for my testing in development, but unfortunately this fix cannot be applied on production sensors, for privacy reasons (Bluetooth Addresses & Privacy in Bluetooth Low Energy | Novel Bits)

Now my next question is, could the Connect IQ Library be updated to work with these randomized addresses?

Thanks for your help, with the above documentation I found the 'bleno' library and used it to further debug the capabilities of our sensors in combination with the Watch.

Now I can fairly certainly say that the issue is with randomized Bluetooth Low Energy addresses.
After updating the sensor firmware to disable the randomized address it showed up in the scanner right away.

This fix is okay to use for my testing in development, but unfortunately this fix cannot be applied on production sensors, for privacy reasons (Bluetooth Addresses & Privacy in Bluetooth Low Energy | Novel Bits)

Now my next question is, could the Connect IQ Library be updated to work with these randomized addresses?

That is pairing in the FW and not CIQ.  

Thanks, I've seen your answer, good to know that you get the same result on your side! What I don't understand then, is that I am able to pair my regular heart rate monitor with my Fenix 5 over BLE... How can it be possible if the Fenix 5 doesn't support BLE ? Or maybe it is a specific BLE issue with this device model ?

The Fenix 5 doesn't support CIQ BLE.  The f5+ devices do. I have the f5 as a device that shows what happens with devices without BLE, but you are the first person to notice it.

I fully agree with you, randomization is a big issue if you want to connect such a device to your Garmin... I am not able to connect my device natively because it has randomization and I hoped that using Connect iQ could solve this issue but it seems it is not the case... I wanted to verify with Jim's app but it doesn't work on my Fenix 5... Did you tried Jim's app on your side ? I don't want to have to buy a Garmin Edge X30 head unit just for checking this point if it doesn't work afterwards...

With CIQ, things are not learned over a connection.  Services and characteristics must be defined in the app's BLE profile.

How are you communicating if you aren't doing a pair request and waiting for a connection?  Then there are things like the 22 byte limit for reads.

Sound to me that unless there are changes made to the sensor, you won't be able to use CIQ.