retunr/enter and right shift not working after update

after the latest os 10.9.5 update my enter and right shift key suddenly stopped working, in the keyboard viewer it doesn't even recognized when i tap them, and when i connect an external keyboard everything works fine. no spills, no dirty, nothing sticky on the keys,it's getting really annoying, i've already tried the speech, accessibility options, and everything i could find online but nothing seems to work, i don't have the installs disks so i don't think i can go back to snowleopard to see if that'll do, so i'm starting to think is indeed a hardware issue