If you are downloading the app for the first time and if you are using iOS 9 or newer, then after the app finishes installing, please:
Step 1 - Go to iPhone Settings
Step 2 - Go to General
Step 3 - Go to Device Management
Step 4 - Choose Notre Game s.r.o. and press "Trust Notre Game" and confirm. (Otherwise the app can't be launched on your iPhone.)
Android Installation Notes:
Please enable third party Apps installation in the settings of your phone.
Step 1 - Go to Settings.
Step 2 - Go to Security.
Step 3 - Scroll down and check “Unknown sources” box.
Step 4 - Tap ‘OK” when it show the warning.