why is the api not accepting the new key, I'm getting the "No API key provided." error

Hey, yesterday night I was able to use a key on my app no problem but this morning, my app stopped recognizing it. I tried to generate a new one and it still didn't work. I tried to use an old key that I generated and it works but is still in the trial and can't work with any calls at all. Any help or tips would be appreciated.