Help please: Ring Doorbell Pro continuously goes offline after updating its internal software

Hi, We've just had a Ring Doorbell Pro installed by a professional in the UK, the doorbell is receiving the right voltage and has good wifi signal strength, after installing the doorbell does an internal software update and then goes offline. I have gone through the process of reconnecting it, rebooting it, reinstalling it, with exactly the same outcome. Any help gratefully received Kind regards Mark