Heart rate monitor loses communication

The heart rate monitor of my partner’s garmin edge 530 is working fine till he get up to 170ppm and then it just go’s blank sometimes it comes back after a few minutes but not always. This started happening after he conected his edge with the mobile app.
We first changed the battery on the heart rate monitor.
Then I bought him a new heart rate monitor it keep happening no matter what we try.

We have checked all the firmwear and lates software as well. How do I un install the software and reinstal it.
Or how do one do a hard factory rest

Do you mean the data isn’t appearing on Zwift or the Edge?