Thank you @wendyg51799511
You screenshot helped me understand. The current design of the LR iPad app requires Lightroom to be in full screen mode for Lightroom's in-app camera to work. The camera will not function in iPad split-screen or slideover modes. Apologies for the inconvenience. I'll ask the developers if anything can be done, but I suspect no change will happen any time soon.
Thank you Charlie! Yes, that worked. As soon as I expanded to full screen, the camera button was accessible. Kind of tricky to figure out! So I appreciate your help. It would be very helpful, for others, if the developers could make the error message clearly state the requirement to expand to full screen.
Again thank you! And have a wonderful day.