How can keep the Magic Jack app active?

[Android Central Question]

I have a Zenfone 3 Laser running Android Nougat.

If I open the Magic Jack app and not use any other phone function, the app will remain open and I can receive calls and messages. However, if I use any other function such as Google or any other app, the Magic Jack app closes, which makes it virtually worthless. I have disabled battery optimization which did not solve the problem.

Neither Zenfone nor Magic Jack tech support had an answer.