Player volume not changing

Hello, I am very new to AI and currently attempting to create a minimal sound file player.
I am using a Motorola G8 power running Android version 11 as AI companion.

Somehow I do not seem to be able to adjust the volume of the files being played back either by using a slider as interface or entering numbers in a number block to set the volume.

I have looked at a few videos and tutorials which seem to be using the same method that I have applied and I now ask for your advice! Many thanks for your time.

What properties have you set for the slider in the designer?