Polar H10 HRM not connecting

My Polar H10 HRM (Firmware updated) and for some reason the App (Either on my PC or My iPhone) does not seem to pick up the monitor on a consistent basis. Firstly it can take ages to detect and when does it then shows it has not signal! If I walk out of the room i can then pick up a signal but not always. Note I have two H10 and it happens on both (Also the on two different windows 10 PCs and Iphone8 - All fully up to date) and I had similar issues on another HRM device.
As a side note it connects to the Polar apps, TSS, The Phone itself. It can connect to a laptop, and also to Garmin 935 and Garmin 235 all in the room.
Is it possible to open a call?