First of all, you should gain weight in training, because it is difficult for your body to make new changes after adapting to the weight, so you can gain weight appropriately, which can be increased on the basis of 2.5 kilograms. Be careful not to blindly increase, so as not to get out of control. Remember to take precautions when you gain weight. Then try to change your training action, because if you keep doing this action, your body will adapt, and changing the action can change the training angle and seek new excitement. For example, you usually do barbell bench press, now you can try dumbbell bench press more, which is more exciting and more difficult.
Secondly, I think diet is more important, and diet should be more important than training. If you feel that your body hasn't changed and your strength can't go up, you can try to increase your intake of protein and carbohydrates, especially for people who are thin and gain muscle. Only when your body has enough energy can you make new changes. And pay attention to the process of letting the body rest. We can stop training for a week and slow down, so it will be better to get back into training.
Finally, many people think that they have entered a bottleneck period when they feel that their bodies have not changed. In fact, it's just that you don't train seriously and don't pay attention to your diet. Many people can't reach the bottleneck at all. So check whether your training is in place, and don't blame yourself for entering the bottleneck period.