Physical Trackpad Button Unresponsive White MacBook

Hi,

A few days ago all of a sudden (and I do literally mean all of a sudden!) the physical button click on my trackpad stopped working. No spillage, drop or damage!! I can tap to click and move the mouse pointer around but anything to do with pressing the trackpad button down doesn't work (such as dragging).

I've read it can be the battery expanding in it's old age - this is not the case as I've removed the battery and powered computer up.

I also that the screw adjusting sensitivity needs a turn - tried that.

Also blasted compressed air into the sides of it to remove dirt and what not.

Late 2009 White Polycarbonate MacBook A1342.

Any Ideas? Looks like I need a replacement.

Thanks!