You will sometimes need to 'allow' your camera to use your phone to do the online ID process.
Close down all other open windows you may have on your phone first, you may have too many open. You can also try switching your phone off and then on again to reset after you have checked the below.
Go to your phone Settings, here are various makes and what to follow to find your camera and ensure it is switched to ON or Allow, then try again.
Samsung:
Settings > Apps > Internet (Samsung Internet/Google Chrome) > Permissions > Camera [ON]
iPhone:
Settings > Safari/Google Chrome > Camera [ON]
Oppo:
Settings > Security > App Permissions > Select Internet browser (Chrome) > Camera [ON]
or Settings > App management > as above
Xiaomi:
Settings > System Apps > Chrome/MI Internet (ask for their phones default internet) > App Permission > Camera [ON]
Nokia:
Settings > App and Notification > Chrome > Permissions > Camera [ON]
Huawei;
Settings > App and Notification > Chrome (ask for default internet browser) > Permissions > Camera [ON]