Unable to use App Store

I am currently using a macbook pro, mid 2012 that runs on OS X Yosemite, 10.10.5. Whenever I try to download anything from the app store, it tells me to sign up, and when I do it says that my Apple ID or password is incorrect. I have reset the password for my Apple ID multiple times and have used this same Apple ID and never had problems with it until now. Ive logged out of my Apple ID and have signed back in multiple times as well, I don't know what else to do from here.