Stopped connecting to HRM Run

I have my HRM Run connecting to my Fenix 6x pro and my Edge 530 via Ant+. 

It’s worked fine for as long as I can remember until yesterday. No matter what I did, the edge would not take a reading from the HRM Run at all. However, the Fenix 6 did. 

I tried restarting the edge. I uninstalled the HRM Run from the age and tried to search for it again - nothing. But at the same time, the Fenix was seeing it and connecting to it. 

I disconnected the Fenix and tried again. Still would not work. 

Any ideas anyone? I love my edge, but it’s useless without HR readings and broadcasting HR data from my Fenix WHR is not as reliable as the strap. So I’m keen to fix it.