For exercises such as "Phonetic Training," as well as creating and forwarding tasks such as "Speak," you must allow the browser to receive sound from the computer's capture device.
To make sure the recorder is on and running, right-click the speaker icon in the lower right corner of the screen and select "Recorders."
Sound device icon
In addition, the list of all recording devices is displayed in the window that appears. If green words appear in the active microphone when the voice is spoken to the active microphone, it indicates that the device is connected and functioning.