Shiny Select Input Improperly Formatted

Hey everyone,

I'm running into an issue I've never seen before with Shiny. I currently have a built out shiny app that utilizes the default styling of the select input dropdown in several locations. Recently, I have found a need to build out a second shiny app with similar functionality, which involves copying over a lot of my existing code. However, when this code is copied over, the select input dropdowns are no longer formatted in their default style and are not callable by the input$ID command. Below is the code I am using to call the select input dropdowns.

selectInput("editSample_SampleType","Sample Type",choices=sampleTypeList,selected=sample$SampleTypeID,width="100%")

And here is a screenshot of what the UI looks like.


Here's a screenshot of what that same code produces in the original shiny app.


Has anyone run into this issue before, or know where I might be going wrong? Any help would be greatly appreciated. Thank you!