Scanning for Network Devices

Hello!

I'm trying to set up the Network Devices scans in Defender under Assets > Devices, and it is just not working at all.

From what I've learnt, there is a "passive" discovery that all onboarded devices will be listening for network devices and they should be then shown in Network Devices.

I could see them several weeks ago (months maybe)... but can't see anything there now.... I believe I have all set up properly... Managed to install network scanner for active probing which works fine (found aruba and cisco devices using SNMP), but the passive listening not working as expected.

What do I miss here? Was there any change in the default behaviour that affected the functonality?