My air protocol drone keeps leaning and won't take off, how do I fix it?

There might be some fur or hair caught in the one propeller which would slow the propeller's turning speed down. A propeller might also be bent resulting in not enough lift (your drone should come with spare propellers). Also make sure that the propeller is turning the right way so that it wants to lift instead of push down. You should also be able to adjust the trim (fine tuning for stability in the air). Make sure to read the manual about the trim and there also might be a section about troubleshooting that might have that issue in it. Hope you can fix it with these potential problems identified!