Shinymaterial SSL CA cert error inside Rstudio but not from bash

[FlorianW]

Hello,
I am working on a small Shiny app where I want to use the shinymaterial package. The problem is the following:
When I want to start the app with shiny::runApp() or simply run the whole code within app.R I get the following error.

Warning in file(con, "r") :
  URL 'https://fonts.googleapis.com/icon?family=Material+Icons': status was 'Problem with the SSL CA cert (path? access rights?)'
Error in file(con, "r") : 
  cannot open the connection to 'https://fonts.googleapis.com/icon?family=Material+Icons'

Strangely the app runs totally fine when I start it from bash with Rscript app.R.
Here is a small example where I get the error

library(shiny)
library(shinymaterial)

# Wrap shinymaterial apps in material_page
ui <- material_page(
  title = "Basic Page + Side-Nav with Tabs",
  nav_bar_fixed = TRUE,
  # Place side-nav in the beginning of the UI
  material_side_nav(
    fixed = TRUE,
    # Place side-nav tabs within side-nav
    material_side_nav_tabs(
      side_nav_tabs = c(
        "Example Side-Nav Tab 1" = "example_side_nav_tab_1",
        "Example Side-Nav Tab 2" = "example_side_nav_tab_2"
      ),
      icons = c("cast", "insert_chart")
    )
  ),
  # Define side-nav tab content
  material_side_nav_tab_content(
    side_nav_tab_id = "example_side_nav_tab_1",
    tags$h1("First Side-Nav Tab Content")
  ),
  material_side_nav_tab_content(
    side_nav_tab_id = "example_side_nav_tab_2",
    tags$h1("Second Side-Nav Tab Content")
  )
)

server <- function(input, output) {
  
}
shinyApp(ui = ui, server = server)

and my sessioninfo:

R version 3.5.1 (2018-07-02)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 18.04.1 LTS

Matrix products: default
BLAS: /opt/microsoft/ropen/3.5.1/lib64/R/lib/libRblas.so
LAPACK: /opt/microsoft/ropen/3.5.1/lib64/R/lib/libRlapack.so

locale:
 [1] LC_CTYPE=de_AT.UTF-8       LC_NUMERIC=C              
 [3] LC_TIME=de_AT.UTF-8        LC_COLLATE=de_AT.UTF-8    
 [5] LC_MONETARY=de_AT.UTF-8    LC_MESSAGES=de_AT.UTF-8   
 [7] LC_PAPER=de_AT.UTF-8       LC_NAME=C                 
 [9] LC_ADDRESS=C               LC_TELEPHONE=C            
[11] LC_MEASUREMENT=de_AT.UTF-8 LC_IDENTIFICATION=C       

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] RevoUtils_11.0.1     RevoUtilsMath_11.0.0

loaded via a namespace (and not attached):
[1] compiler_3.5.1 tools_3.5.1   

Any suggestions on how to fix this are greatly appreciated.