I've fixed it! Though it's absolutely ridiculous and I will definitely
be making a complaint to Google...... I used an iPad Air 2 that I've had
for years to set up my cameras and the doorbell - lo and behold, they
worked straight away, live view work...
I should also add my partner can't see live video either, and we can't
view the cameras on our Nest Hub. I've got a Pixel 4 XL and she's got a
Pixel 6 XL - we use Google WiFi.
I have the exact same issue, just bought two brand new Nest Cameras
(Battery) and live video doesn't work for either of them. I've tried
resetting the cameras, restarting network, etc, nothing fixes it.