When people aren’t gaining any muscle, it usually has something to do with their diet or workout routine.
If your diet is on point, but you still aren’t putting on the muscle mass that you should be doing, this video goes over the proper ways of lifting weights. You need to be training to your max intensity and push your body’s limits, lifting until failure.
You must maintain good form when you lift and the end of each set should be you lifting as much as you can physically handle. You need to push yourself and try to lift more with each set. Good form is important of course as you do not want to injure yourself, as poor form will do more harm than good. Get your form down correctly and then increase your weight as you workout.
So together, a strong diet, pushing yourself in your workout routines, and you will achieve better results.