Battery Pack for ring Siren showing incorrect status display

Hello, I recently installed a ring Alarm system. It was very easy and I have been impressed by how much I can configure the system to suit our needs, But I am having trouble with the ring Siren. I purchased a battery pack and an external hard wire power supply for the siren as it is sited high up on my house and I want to be certain of minimum maintenance. The battery pack was fully charged over about 10 hours and showing a solid green light before I installed it into the siren. I then installed the siren as per the instructions. But... the siren display in the App does not show the Battery Pack as being installed. There is a line through the pack (and also the D Cells but these are removed so that bit is correct). With the hardwired power supply switched off the alarm still reports as being on line and the test siren also works, so the battery pack is clearly working. But the status display shows the pack as missing. Also - under power options the battery pack is shown as 'not connected'. There is nothing in the event log about either power source other than the D Cells showing (when I first tested the siren on the bench I used the supplied D Cells). I have tried removing and re installing the siren but with no success. Am I doing something wrong or is the siren faulty? Thanks.