Option Right click dragging mouse does not work to change size/hardness of the brush tool

Hello everyone,

I am trying to find out why the shortcut to change the brush size/hardness is not working.

Option key + right click + dragging the mouse does not work. 

I feel like I've tried everything (every keys on my keyboard, even installing previous versions of PS...).

I am using a French keyboard (Azerty). I mention it in case it can impact the shortcut...

Any help welcome.

Thanks!

Maxence