Running App from peakfq::peakfq_app() doesn't work

When I try to launch the Shiny App by running the peakfq::peakfq_app() function, I've started getting the following error:

> peakfq::peakfq_app()
Loading required package: shiny
Warning: package ‘shiny’ was built under R version 4.3.2

Listening on http://127.0.0.1:7215
Warning: Error in shinytheme: could not find function "shinytheme"
  64: bootstrapPage
  63: fluidPage
   2: shiny::runApp
   1: peakfq::peakfq_app [C:/ssiefken/peakfqr/R/app.R#51]
Warning: Error in shinytheme: could not find function "shinytheme"
  64: bootstrapPage
  63: fluidPage
   2: shiny::runApp
   1: peakfq::peakfq_app [C:/ssiefken/peakfqr/R/app.R#51]