Formatting looks fine in viewer, but broken on shinyapps.io

Maybe this is a naive question - first time building or publishing a flexdashboard.

I have a pretty simple flexdashboard.

The YAML is as follows (hmm... doesn't print properly - but is properly formatted/indented in my code)

title: "EB Outcome Dashboard"
output:
flexdashboard::flex_dashboard:
orientation: columns
vertical_layout: fill
horizontal_layout: fill
runtime: shiny

Then there are two columns
Column {data-width=275}

Load Data - Choose Surgery

...followed by some code with a fileInput, selectInput, and a checkboxGroupInput, then

Column {data-width=750}

Outcome

...followed by some code with a renderPlot element.

That's the whole thing. When run locally, it looks like this and everything works perfectly.

But after publishing to shinyapps.io, the formatting is all gone. The selectInput doesn't appear, the second column with the plot doesn't appear, the checkbox input is over on the rhs of the page, etc...

Any thoughts?

Sorry - I'm having a helluva time trying to edit/format that post (Error 42). Mea culpa.

Anyway - here's what it looks like on shinyapps.io