Motion sensor too far away

@ victoria_115 try putting your system in test (from the keypad) and then go out and press the test button.  Make sure the voice setting is on high and have someone stand near the base to hear it. If should say "motion sensor". Another way: place your system in test, arm it and walk into your garden room and siren should go off. And make sure your motion sensor is set to instant trigger, and when you arm the system, do not enter the room for about 3-4 minutes to give the motion sensor time to "read" the temperatures in the room.
My guess it is working fine.

@victoria_115 says: may be worth changing the battery and/or trying another motion sensor in that area to see if it works okay.

No massive thick walls but steel siding or anything like that?

Right, the range of the sensors should be about 800ft over open air. But both wireless and physical interference can severely impact that - especially metal, or maybe mesh insulation.

- Johnny M.
SimpliSafe Home Security