I’m having this issue too. I have data saver turned off but it’s still not viewing through wifi. I can view the cameras through my PC hooked up to the LAN using the Ring app in the microsoft store.
If I put my router in access point mode it works, so that’s a workaround. Still don’t like having my router in ap mode as I can’t have some of the features enabled.
I’ll be testing it out tomorrow on my wifes Apple phone.
I even tried creating a guest network and connecting the doorbell to that network, no dice. 
Here’s the crazy thing, This only happens when I’m using AT&T internet…
I tried through t-mobile hotspot, works like a champ.