Hi Buch,
Thank you for contacting us. I'm not sure what error message you are referring to here. Can you write out the words in the message for me? It's possible that mSecure 5 won't be able to be installed on a device running a very old version of Android, and I suspect that's what's happening here. When you say Android 6 phone, do you mean that the phone is running version 6 of the Android OS?
Butch