Trojan

I have recently changed a Optima compact Gen 4 panel as a favour for someone. The first panel that was bought through Amazon had a fault on it. A second unit has since been fitted and all is working except the new Siren which is a Reson 8. The unit comes with pre-fitted links across TA TAMP and PA. The manual states that these should be in place when powering the unit up. This contradicts some advice on online instruction that says to remove the link to T A when wiring the siren. The external siren does not sound or flash when an alarm is activated, internal sounder in board works OK and all zones work fine on a walk test. No LED,s in the siren are visible either. I have a few possible ideas, ie the fuse or the internal battery in the siren and did not have a tester on site to check voltage. The house is about a 60 mile round trip so I need to go prepared for possible outcome. Can anyone help, thanks