MBP trackpad won't click

[Bobcat16]

So I have a Macbook Pro unibody, bought when they first came out in the summer of 2009 (not exactly sure what model it is...maybe 2 versions ago). Anyway, everything works fine on the trackpad except you can't click on anything. Scrolls fine, no water spill or anything. Any suggestions on trying to fix it before going to the Apple Store? I can click with an external mouse to navigate if need be.

 

[Bobcat16]

Anyone have a similar situation?

 

[Heavertron]

if the battery swells due to failure or impending failure, it can stop the trackpad from clicking. Best check out your battery.