The easiest fix is simply restarting or reinstalling your browser.
To manually enable your mic/camera on...
Select the lock icon to the left of your address bar. A pop-up will appear with a list of options. Make sure Allow is selected under Camera and Microphone.
Select the lock icon to the left of your address bar. A pop-up will appear with a list of options. Select the arrow to the right of WWW.RABB.IT.
Then select More Information.
A different pop-up will appear. At the top, you'll see several buttons. Select Permissions.
This will bring up a list of permissions for Rabbit including the CAMERA and MICROPHONE. Uncheck Use the Default and select the button Allow to force your browser to allow your microphone and camera to be used by Rabbit.
Select the camera icon to the left of the address bar. If it's grey, this means the camera and/or microphone is being blocked by Opera. A pop-up will appear with an option to Clear this Setting and Reload.
A pop-up will then appear asking whether you want to allow Opera access to your Camera/Microphone. Click Allow.
If you don't see this option, enter: opera://settings in the navigation bar.
This will bring up your settings and preferences:
On the left sidebar, select Websites then scroll down until you see Microphone and Camera.
Make sure Ask me when a site... is selected. If these buttons are already selected but your camera or microphone isn't working, try switching between them. (Make sure Ask me when a site... is selected before you leave.)