Hi TKSharpless,
this is because only one camera is selected. You need to select all cameras. It is possible by different ways, but one of them is Select All tool, which can be find under SCENE 3D/TOOLS/Registration & Sparse Point Cloud/Select All
You can also select all cameras in 1Ds view/Images using the same way like selecting files in folder (for example CTRL+A when one image is selected).