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If you have enabled editing on the layer, then you won't see the dropdown options. This is because editing attributes requires that the popup display as a simple list of attributes, with text input boxes next to the field name for editing. The user interface isn't sophisticated enough to manage both an editing popup and a non-editing popup. This is something we want to address in the future.
If you don't need the layer to be editable, you can disable editing and you'll see all the popup options. If you need to edit attributes, disable editing first, then configure the popup, then enable editing. This should work.
Thanks,
Mike