Anyone using a Viiiiva HRM with the mobile app - BLE or ANT+?

Tried it out today but the app did not see/connect the HRM on either Bluetooth or ANT+ - is this something others have had success with?
The HRM connects ok to other apps such as Viiiva’s and EliteHRV and is a BLE device.
I have also set up an ANT+ dongle with the phone and could connect the Viiiiva that way using the ANT+ software from the Android play store.
I also connected an old Garmin ANT+ (the old kind with the large plastic body) HRM to the phone and that too could register my heart rate using the ANT+ test software but was way out in its measurements.
Neither HRM seems to generate a reading on the BPM counter on the Xert mobile app - but both were detected by the app and connected using the scan menu item, over ANT+. No connection over Bluetooth.
Xert Mobile and Tacx Neo connect ok over Bluetooth so the app is seeing Bluetooth devices successfully and displaying the data.

Am I doing something wrong - any advice?

Phone: Pixel
Android: 7.1.2

PS: Is there a way to search this forum?

User error it turns out.
After a few retries it did recognize the Viiiiva BLE HRM - but just showed an HR of 235 constantly, when connected via an ANT+ dongle it worked fine and the app also saw that it could bridge other devices. This is fine for indoor training.