Working fine on my Note 4 under Android 5 and 6. As already posted, you will get a black screen if you open another instance of the app on your phone, just use the task list button (the button to the left of the home button) to bring up your recent apps and select HiControl from there if it is already running. If not, it should be working ok.
If you have a black screen 100% of the time i.e. you can't get the app to work at all, there must be something else wrong.