Mute button iPhone 11

Try and Force Restart your iPhone EXACTLY as shown below and see whether that resolves the issue:

• Press and quickly release Volume UP button
• Press and quickly release Volume DOWN button
• Press and Hold the SIDE button until an Apple logo appears and then release the Side button (Can take up to 20 seconds. (DO NOT release Side Button when invited to Slide Power OFF). 

Axel F.

Which mute button are you referring to? Can you specify? Is it the Silent button that is on the LEFT side of the iPhone or is it the Mute Microphone option during phone calls?

Axel F.