Wired Ring doorbell won't start up

I have a brand new wired Ring bell. Wired up all fine, did firmware updates and it was all working, sound and picture fine and app showed good power. Turned the power off at mains to do other work and back on and the doorbell is dead. It fires up, blue flashing lights, plays a sound, then cuts out and goes black. This then repeats over and over. Tried to reset by holding in button, no joy.Its currently sitting on my desk as the noise from the reboot startup tone was getting annoying. Do I need a new bell?