Do you have the boxes checked on your photoshop brushes? So that your pen pressure works? Because I know some people forget to check those boxes or just didn't know that you had to.
You could also try reinstalling your driver or (I don't know how to do this on a mac or if you even can, but on hp you
> press your windows key
> "services" n click on it, it'll have an icon w/2 gears
> scroll down 'til you find "Wacom Professional Tablet Service"
> select it, then hover over it and right click
> click on "Stop", after it loads and stops right click again and click on "Start"
I imagine there's something similar to it on mac though and you could probably find a way to work it out on there or research how to do so?
you could also try removing all ur tablet preferences and then restoring them to see if it fixes itself