Unable to install any device (Ring alarm 1st gen)

Good morning and happy new yearI'm trying to install a second hand ring alarm I've been gifted by my brother, but I'm having trouble with the base station recognizing the sensors.This is a 7 piece set and first generation. Only one contact sensor still had the plastic tab and was the only one recognized by the base station - no other sensor, keypad was.As per the app I tried to remove the batteries on each sensor and put them back in one by one close to the base station but still had no luck.My brother has already removed the base station from his app.The ring alarm is working right now, but only with the contact sensor at the main door, I would really like to install the keypad and movement sensor.I'm really out of ideas and I was hoping I could get some help here.Thank you so much for your time