In addition, the Duo app will not switch to video view if the receiving recipient does not unlock the device. If the phone is locked, a small message appears telling you that the device must be unlocked to start a video call.
The caller will receive a message mentioning that the recipient is not available to receive video calls. Calls that switch to video chat on Duo will appear twice in the phone call list. One as an original phone call, and another as a call to video chat Duo. This
new feature will start rolling in to users of the Google Phone app, and
will be rolled out to all users of the app regularly.