I have learned some about this ... It looks to me as if the admin document is loaded into an iFrame, and the headers need to be set so that camera access is allowed from the iFrame.
Some excerpts from official Mozilla pages:
Media() is a powerful feature that can only be used in secure contexts; in insecure contexts, navigator.mediaDevices is undefined, preventing access to getUserMedia(). A secure context is, in short, a page loaded using HTTPS or the file:/// URL scheme, or a page loaded from localhost.
... User permission is always required to access the user's audio and video inputs. Only a window's top-level document context for a valid origin can even request permission to use getUserMedia(), unless the top-level context expressly grants permission for a given <iFrame> to do so using Permissions Policy. Otherwise, the user will never even be asked for permission to use the input devices.
Info on the Permissions Policy (used to be called Feature Policy)