How can I fix my house alarm?

Have replaced the existing house alarm sensers with Activ8 PIR,s. The old system had green/white as the supply, blue/yellow to Tamper and red/black to alarm. The Activ8 has supply, tamper and relay terminals so I wired the green/white to supply, blue/yellow to tamper, red/black to relay. Everything seemed OK with LED operating on motion movement, Tamper when the unit was opened up, alarm appeared set when code put in however there was no activation of any description when room was entered, where have I gone wrong.