Rendering mapbox map in RStudio Connect

I have been trying to publish a flexdashboard to RStudio Connect with a tab containing a map created using the mapbox package. The dashboard runs locally and shows the map as expected, but when I publish to RStudio Connect, the resulting map will not load:

Does anyone know how to troubleshoot why a mapbox map wouldn't render on RSC? For a minimal reproducible example, here is a dummy dashboard I built. I have set my MAPBOX_TOKEN as an environmental variable, but still can't get the map to render on RSC.

---
title: "Test map"
output:
  flexdashboard::flex_dashboard:
    orientation: rows
    vertical_layout: fill
runtime: shiny
---

```{r setup, include=FALSE}
## packages
library(tidyverse)
library(janitor)
library(usmap)
library(plotly)
library(DT)

Sidebar {.sidebar}

selectInput("states",
            label = "States:",
            choices = c("DC", state.abb),
            selected = c("DC", state.abb),
            multiple = TRUE)

Provider map

plot_mapbox(data = maps::us.cities)