Good day. I found the solution to my problem, which I'll share and hope that it solves yours.
Under Admin > Account Management > Account Settings, you will see a menu across the top consisting of "Meeting...Recording...Audio Conferencing...Zoom Chat...Zoom Apps...Whiteboard". Under "Whiteboard", the bottom section is "Whiteboard cloud sharing". Mine was originally set to "Only users in the same organization". When I changed it to "Allow sharing with anyone with a Zoom account", I was able to share my whiteboard with everyone.