It means that the web dialer is trying to access the microphone and camera to make calls from the web, but nothing has worked. The problem can happen because of 2 reasons:
- you have not provided the required permissions to your browser;
- you do not have an encryption certificate for the server.
The solution for the 1st reason is to provide access to the microphone and camera in your browser settings.
For the other problem, you are required to have a certificate signed by a public certificate authority. You can easily get this certificate from the the Let's Encrypt.