We have been working on a program to make our robot turn a corner,And yesterday we had the program where it was turning the corner successfully,But today we opened up the same program from yesterday and it did not perform correctly.We have changed out the motors and that is not the problem.Our question is why is the same program that we used yesterday not working today as it did yesterday? What could be the problem? And how do we fix it?

Could you please provide your code so we can see what your robot is trying? There is no real way for us to help you without some idea of what your code is trying to do. It's not always the same as what *you* want your code to do.

- Xander

We used to have that kind of problem a lot in FLL. It is usually a result of changed battery power. You probably charged it overnight. If you didn't, the power will be lower than yesterday anyway.
Always remember to charge your batteries! But even this can be inaccurate,so try using robotC's PID control and the encoders to reduce the dependency on battery power.

We have found out that it was the battery life that changed the program,Thank you for your assistance!