My Border Collie no longer listens well. Any idea?

My border collie is 7 years old and I have had her since she was a puppy. She has lived outside in a kennel until about 2 years ago. Now she is a house dog. She used to listen well and be easily trained. She still is trainable. She just doesn't listen very well. Sometimes when I call her she just ignores me, starts coming and then drifts off, doesn't come at all, or even goes the opposite way. I have tried a lot of things. Nothing has permanently worked. Just sometimes temporary. She stays in the house only going outside for potty breaks. She occasionally gets played with outside. What should I do?