Hi,
Sorry for huge delay in responding (I doubt receive a notification of a reply so missed this). I have managed to fix this by changing the delay to 180s. Basically the issue was that I was going upstairs at night and then arming “home”. This should activate all downstairs sensors. However, unless you wait 180s for all sensors to clear they will not arm.
I think this is a really important point that Ring should make clear to people. I reckon there must be lots of people leaving their house and arming immediately and they will have no idea some of their sensors are not armed as they haven’t left 180s for the latest motion detected to clear from the system.
Anyway, hope this helps anyone who may have had the same issue!