"I added and saved a block, but can't see anything on the published page"Browser Info Environment
The default template for Front End File Uploader floats an icon above the top right of whatever block follows.
If you only have one FEFU block in an area, it may be that the default floating icon is off the bottom of the area. It could also be hidden behind something with a higher z index.
If you can't see the front end icon on the published page, you can try the 'unstyled_link' template to confirm that the block is rendering and behaving as it should.
Having confirmed the above, you can then try adding another block below the uploader (perhaps a gallery it is uploading to), or make a decision on what template and styling you need.
In retrospect, with the above knowledge I would have made the unstyled link template the default view for this block. However, to do so now would create a problem for too many existing users.