Ring Doorbell 3+ will not connect to Chime Pro Network

Hello, I am having problems connecting Ring Doorbell 3+ to Chime Pro Network as I need the wifi-extender functionality, I hope you can help. The Chime Pro is connected successfully to my home wifi network, this is ok, but then this is the sequence of events:- Launched app (iPhone)- Selected ‘Devices’- Selected ‘Chime’- Selected ‘Chime Pro Network’- Selected ‘Ring Doorbell 3+’- Selected ‘Switch to Chime Pro Network’- Pressed and released the orange button on Ring doorbell, lights spin, doorbell device 'voice' confirms it is in setup mode- Confirmed in the app by pressing ‘ The light is spinning’- Chime Pro 'voice' confirms is looking for Ring device, finds it, says Ring device is set up and connected to Chime Pro- After a further minute, Chime Pro voice confirms “Now connected, with Ring you are always at home”- However, during this time, the Ring App stays stuck on the step ‘Connecting your Ring Doorbell to your Chime Pro Network’ and eventually times-out with the message ‘Your Ring Doorbell could not connect to your Chime Pro.....'- In the app, I go back to Devices\Ring Door Bell and check ‘device health’ and the doorbell is still connected to my home wifi network.So in summary, it seems the Chime Pro confirms a connection but the process still it does not complete.Note I have tried moving the Ring Doorbell very close to the Chime Pro and have the same problem.Thanks in advance for any advice.