Motion sensor from security system not connecting

Ordered 8 piece Ring Security system. All devices set up with no problem except motion sensor that came in the primary box. Pulled tab but it did not connect to base. Removed battery and re-inserted, didn't work. Googled other ideas, reset motion sensor and tried again, didn't work. The 22nd motion sensor that came as part of the 8 piece system connected just fine. Need help please. How can I return for a replacement when it was in kit.