Hello  @RicardoAAG 

It's a great step to confirm the Microphone on is the maximum on Camera's live page.

Please also confirm that your phone or tablet has the large volume, and check if the volume is normal when you stream videos on a different app? 

You can also factory reset the camera and see if that makes any difference: https://www.tp-link.com/us/support/faq/2705/

May I know when did you purchase the camera and when did the issue start? Can you help provide a video clip showing the low audio. 

You could also consider getting a replacement under the warranty if the above does not work.