frozen touchpad on Mac Air

Friends, I am new to the forum and apologize if this is something already addressed. I have a three-year-old Mac Air. The device's touch pad seems to be frozen--I can swipe, expand the screen, but cannot left- or right-click, which means I have to use a mouse.

Any suggestions? Has anyone had this happen before and is there a fix?

Thanks,

Check to see if your battery is swollen. When batteries swell, they press up on the bottom of the touchpad. Happened to me on a 13" MBP.