Here’s my guess. Circles, lines and shapes in a decal are outlines in cam settings. Your mounting holes are probably on top layer. It
would make sense that top outlines are turned on for top assembly layer but not the bottom. I have recently started working with connectors that overhang the board edge. I draw full outline on top assembly layer and partial on bottom assembly layer. In gerber file I need to show outlines for top and bottom mounted components for these to show up correctly.
I already had outlines turned on for both top assembly and bottom assembly in the CAM setup, see screenshot. This is the way both top and bottom assembly was set, so why are the assembly bottom 3 mil circles inside the mounting hole decal itself not photo plotting? By the way, I solved the problem for the moment by adding the assembly bottom 3 mil circles on the PCB itself (i.e. NOT in the mounting hole decal). I really don't like doing it this way for obvious reasons, but it does photo plot that way. Why is it not working when the assembly bottom 3 mil circles are inside the mounting hole decal though?
I see it is just what I thought. You have outlines turned on for layer “Assembly Drawing Bottom”. But on the left you are only showing
bottom mounted component outlines for this plot. Turn on the top mounted component outlines and I’m sure you will see your circles.