This behaviour is observable in the documentation: http://semantic-ui.com/modules/dropdown.html#remote-content

To reproduce click the icon located in the right of the Dropdown before remote data has loaded. Nothing happens. Click anywhere else in the Dropdown to trigger the remote data load. Clicking the icon then works.

The issue appears to be in the event handler for clicking the icon, which attempts to toggle the dropdown menu. This is prevented from happening if there are no child options or message in the dropdown, which is the case for a dropdown with remote data.

https://github.com/Semantic-Org/Semantic-UI/blob/2.1.8/src/definitions/modules/dropdown.js#L874-L879

I believe if the module.is.search() is true, it should work more like the text element handler:

https://github.com/Semantic-Org/Semantic-UI/blob/2.1.8/src/definitions/modules/dropdown.js#L880-L885