1. You have not found an exercise routine that you enjoy doing. One that makes you sweat and exercise 3-6 times per week with consistency.
I don't care if it is Zumba on a BOSU ball. You must enjoy it and get up a sweat. Why do you bother if you hate the current exercise you are doing?
There is no exact exercise that gets the best results. If you want to step on a fitness stage then there is no doubt you need to make weight training a key component of your training.
For general fitness and weight loss, anything goes. Find that type of exercise that makes you want to do it.
2. You haven't found a diet that you can stick to and fit into your normal busy life. One that doesn't make you feel restricted, deprived or missing out.
Your method of eating should be designed even for your busiest, most stressful days. Not the days where you think you have time to make Instagram worthy meals and 6 meals per day. That's a joke.
Do not get excited about your friends weight loss if they have a history of trying multiple diets.
I haven't changed my way of eating for 10 years. Can you confidently do that when you consider trying a new diet?
If not, then don't bother. Find a way that suits your lifestyle and one that is simple and so easy to follow that you could explain it to a 5 year old.
Do you have any other reasons why you may not have lost weight? I am keen to hear.