Ring Alarm - Second owner

Good morning all. We recently bought a house and the previous owners left their ring alarm, keypad, motion sensors and contact sensors. I've been able to install the ring alarm base device and connect it to WiFi, but I'm unable to setup any of the contact sensors or keypad etc. I've followed the instructions (remove battery/plug in keypad etc) but it's not registering in the app. Any ideas on what I need to do to install all the ancillary devices?