Looking at your new blocks, I see you Register For Bytes, but you did not include a BytesReceived event to catch them when (and if) they arrive.
That can’t be right.
I can’t find the controls that let me assign this thread to some one else with more BLE Heart Rate Monitor experience.
I suggest you add a post to this thread asking them (@Martin_Wood) to visit this thread Reading BLE service in Appinventor
and help you.
I’m in over my head.