https is not required, but it's recommended.
When does the app hang? Is it when you enter the site URL and click connect?
I just tried with my Android device and I was able to reach the credentials screen. In which device are you trying it?
Please notice that the app will always try to connect using https first (for security). If this connection fails, then it will try with http. If the site is slow to return the error, it can take a while to connect to the site (1:30 minutes max).