Coros HRM connection issues

there are a couple of similar posts but closed with no solution i can see.  really annoying problem with new Coros HRM 

if i add the sensor to my edge 530 sometimes if sees it - i add it but it doesnt connect & so i get no HR recording.

at that point my other connections (Indoor trainer/power) drop constantrly in & out.

i can remove the device, go to re-add it & then it doesnt even see it.

(round & round i go before i give up & train without HR)

i've only successfully recorded once with HR.  it connects to my fenix 6 solar fine & zwift running on android tablet fine.

looking in the coros app on phone under accessories it looks like i'm running latest firmware 1.24 on the HRM & my edge is fully up to date. 

PLEASE can someone help me else i'm going to try & return the Coros HRM & go back to chest strap