I am using the R Package shinydashboard, now the dashboardSidebar is NOT showing in black background

Question

Here is my code:

dashboardPage(skin="purple",
              dashboardHeader(disable =T),
              dashboardSidebar(
                  dateInput("ProjectStartDate", "Start Date",format = "d-M-yyyy", value = Sys.Date()),
                  sliderInput("NumTasksInParallel", "Parallel Tasks", value=6, min=3, max=10),
                  sliderInput("NumPhasesToRegnerate", "Num Phases", value=4, min=1, max=5),
                  actionButton("GenerateProjectPlanButton", "Run", icon=icon("car"))
              ),
              dashboardBody(
                  fluidRow(
                      box(title="Project Plan GANTT Chart", width=12,solidHeader = TRUE,status="info",
                          plotOutput("GanttChartPlot", height="auto")
                          
                      )
                  )
              )
)

It was running fine. But once I upgraded mac OS, shiny package, The left nav is no longer with a darkbackground. And hence unable to see the text. And unable to change the background / font colors

Any help would be greatly appreciated