Ring Video Doorbell (2ndGen) Internal Chime Issues

Hi there, I recently installed a Ring Video Doorbell (2nd Generation). I have hardwired the device and it is receiving power; however, my existing internal chime does not ring when the button on the Ring doorbell is pressed. I have confirmed that the settings on the Ring device are correct and tried various options (e.g. setting it to mechanical or digital chime. My internal chime is a Friedland D792 and I have checked that it is working by connecting the two wires together (which causes the chime to sound). The wiring looks in good condition and my bell transformer is providing 8V which is understand should be sufficient to trickle charge the Ring device and power the internal chime. I have tried the various Chime Connection options in the Ring App but my internal chime never rings. Can anyone suggest what the problem may be? Thanks,