A radar detector is not a police car detector. It’s a radar detector. If a police officer doesn’t have a radar gun in their vehicle (and many don’t) or if they simply aren’t actually running radar and transmitting, there’s nothing for your radar detector to detect and thus it will stay silent.
This is very common.
There have been a couple incidents with my R7 where my “mute memory ” will engage when a cop is shooting KA band somewhere I’ve never been. Are police capable of engaging that on radar detectors?
Disable Ka lockouts if you’re using them