Why isnt my camera on my phone working when I am using InstaID Mobile

You will sometimes need to allow your camera to use your phone to do the online ID process.

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]