Audio issue when I use external video application

Hi I have been usind 6s Plus and also BOTIM video call application which was working fine. Last one week, when I talk over phone normaly the voice gets transmitted. But when I use BOTIM, SKYPE etc., video calls the voice gets transmitted only when I use Hands Free and without hands free when I speak directly the receiver is unable to hear my voice. we are able to see and I am able to hear. BOTIM has been deleted and reinstalled. Can you please help