Microphone didn’t works

When I updated to iPadOS 14.6, the microphone didn’t work during call in apps like FaceTime, Google Meet, Facebook Messenger, Discord etc.

I have found the following problems:

1. An orange indicator is supposed to show up when an apps is using microphone. However, when I use the apps above to call, the indicator didn’t light up.
2. Voice Memos app didn’t work. The recording of Voice memo will end by itself immediately as long as I start recording.
3. Other’s cannot hear me during call, and I can’t hear them either when using the above apps.

I believe that this is not a hardware problem, as:

1. This only happens after I upgrade my iPadOS to 14.6
2. Both of my iPad Pro 11 inch (Gen 2 and Gen 3) and my friend’s iPad Air 4 have the same problem.