Rshiny dashboard broke down with error message 'missing value where TRUE/FALSE needed' (dashboard broke down out of the blue, didn't change anything)

This tells that you have an if statement , and haven't accounted for the possibility that the value evaluated might be missing / NA.

Look at the following code; and before you run it to see what the output is, try to reason about what you expect would happen. Hope this helps.

if(TRUE){
  print("true")
}
if(FALSE){
  print("false")
}
if(NA){
  print("something else ")
}