It is offline because it is an battery device and asleep 99% of the time.
It only wakes up when you activate the door sensor (for just a few small seconds) and on a certain (adjustable) interval, but that is also just 10 seconds.
When it is asleep you can’t send anything to the device cause well, it is asleep.
Both door sensor’s should show it being offline, so it might definitely be a range issue, range isn’t just determined by the distance, also a lot of things nearby can cause interference on the z-wave frequency and the bathroom one just has the luck that it can go through several other devices to get to homey (which it does according your screenshot)
