Accenta Mini 8 / Apollo Series 65 smoke detector problem

[handful]

I have an issue with my Accenta alarm not triggering when the Apollo optical detector detects smoke. I have just had to re-program the system due to having a new front door, I decided to just use the PIR in the hall as zone 1 to save the hassle of wiring a contact sensor to the door and then disabled zone 2. I'm new to this malarkey so had a few issues getting the timed zones set up correctly but have that sorted now. What I'm not sure of now is whether I may have inadvertently done something to the fire zone settings. I've checked everything in the manual, made sure zone 8 is set up and active as a fire zone but if I do an alarm test nothing happens. The sensor is working ok because the red led comes on when it detects smoke. Would one of you kind experts be able to point me in the right direction? The wiring hasn't changed at all since it was last working which in all fairness was some time ago so it may be nothing to do with the recent changes I've made. Apologies for the rambling and thanks in advance for any help!