The problem is, you have to be both using the quilling whistle function and also have turned on whistle smoke. Then since you are using the app- the whistle pull cord must be showing Purple to be in quilling mode for whistle steam to actually work. So yes, a couple of conditions and settings for it to work properly.
Also, double tapping the whistle cord switches it between white mode- normal non quilling, and purple- once you have enabled Playable Whistle under settings. required for quilling and whistle steam to work. Again, this option or feature only kicks in after first under the settings tab enabling quilling and whistle steam turned on.
This is for using a DCS remote. The rules are the same- both quilling whistle and whistle steam has to be turned on- but the "how you do that in the remote" is different than the app. Also, since the remote uses the thumb wheel for quilling, you lose speed control function when using the whistle, where as in the app with the pull cord, you have both functions the speed dial and the pull down cord.
Hence- I find running a whistle steam engine actually better and easier under the app than the DCS remote.