By default, your browser is probably not allowed to use your camera and geolocation. However, depending on the method chosen for signing documents, this access will be required.
Camera Access
When you click on "Take a selfie", a warning similar to the one below will appear on your screen (probably in the upper left corner):
Click "Allow" and the browser will make the camera available for you to take the picture.
Geolocation access
During the signing process, you can also allow browser access to your location and add greater legal validity to the document.
Once you see the document to be signed, click the "Sign" button as usual. Soon after, a warning similar to this will appear on your screen (probably in the upper left corner):
Click on "Allow", so that your browser makes the information about your geolocation available to the platform.