Trouble with Netvue App

Hi, I wonder if anyone can help solve a problem I and my partner is having with the Netvue App? I have a Netvue Belle. I’m in the UK. When the bell is pressed my partner gets the chime notification on her phone but can’t speak to whoever has pressed it. She has an Iphone and the IOS app. On my Galaxy fold3 (Android) I don’t get the chime notification but can speak to whoever has pressed the bell. We have done everything we can think of to resolve these issued and are tearing our hair out. Nothing seems to work. Can anyone shed some light on this?