SipManager.newInstance (this) returns null

Question

I follow the instructions here step by step, but when I want to get a new instance of the sip manager, it returns null!

My LG G4 device is running Android version 6.0. I can run third-party sip applications from a Google game, so that means my device supports sip. but why does this string return null?

SipManager manager = SipManager.newInstance(this);