Probably because, based on your previous question, you commented out
KeyAuthApp.regstr(username, password, key);
Simply commenting out code that causes an issue is NOT a good approach to solving problems. As you have just discovered, it causes other problems.
Before attempting to fix the problem you now have, you need to go back and resolve your linker problem. I quote from OriginalGriff's solution
Quote:
We can't help you fix that, you need to check the KeyAuth library (which appears to most likely be a github thing) and see exactly what it provides or contact the author directly and ask them.