Hi simonwray
Sorry to hear of the problems experienced with the Connect App and connecting to your hub.
As well as the steps offered by newapollo, please ensure the old wireless connection is removed from the phone also as this can cause issues with the app. to do this Go to 'Settings' and then 'Network & Internet'. Select 'WiFi' on the left menu, then select 'Manage known networks'. Select the network you want to remove, then click 'Forget'.
Thanks
Rob