Not working on iPad

Just downloaded the app for iOS but strange enough was that it worked fine on my iPhone but not on my iPad Pro 12.9 inch - it did not load completely and flashed constantly. I've restarted the Wi-Fi to make sure the connection was working. I then tested it on several iPad models (iPad Mini 4, iPad Pro 10.5 inch and iPad Air of my friends and colleagues), it worked on the first two iPads but the same issue on the Pro 10.5. I am wondering if this has something to do with the iOS version since the issue occurred on the two iPads running iOS 11.2 and 11.3. Any suggestions?