My click won't work on trackpad or USB mouse

Recently had to change the SATA cable in my MacBook, and after putting the top case back together quite a few time to make sure the trackpad connection was alright; I cannot click/select anything. I'm currently trying to restart on a new hard drive and I cannot even select the beginning setup options. My trackpad moves around perfectly fine - but no clicking. The same thing happens when I connect a USB mouse and Wacom pad, so I have trouble believing its the trackpad or connection there. Any help?