Mic during video call not working with certain apps
I just bought a new iPhone 6s Plus. I have several calling apps on it such as Facebook messenger, WhatsApp, Viber. When I use any of these apps over a video call, they don’t work on speaker. The person on the other end can’t hear my voice. I have tried turning off the phone, reset the network settings, uninstalled and reinstalled the apps, but nothing worked. The iOS version that I am running is 13.3. It only works on FaceTime. What is the fix for this?
iPhone 6s Plus