I used to be able to kickflip perfectly everytime. But then I just woke up one day and couldn't do them. I cant flip them right. How can I relearn them as good as I did before?

Practice Practice Practice, one thing that could be wrong is you might of created a fear of the trick, or your puting to much thought into it, all in all just practice and let it flow and dont get frustrated with it it will just make it worse.