Hi,
I'm Rodrigo and I'll help you.
The audio from the microphone outputs in the speaker when it is connected to the green aux port on the computer right?
Open Settings > System > Sound > More sound settings > Recording tab > Double click the computer audio device (usually Realtek) > Listen tab.
Do you have the "Listen to this device" option enabled?
If not, go to the Playback tab > double-click the computer audio device > Levels.|
Do you see a "Microphone" slider?