This is the reason why self help books fail to help 90+% of the readers.
Everything in life has prerequisites.
If someone wants to learn Basic Arithmethics they need to learn Numbers first. If someone wants to start a startup, they need to have enough secure run way (funds)
The reason why something is not working is ALWAYS that the prerequisites are not there.
For someone to start losing weight they have prerequisites that need to be fulfilled, giving them advice will bounce off of them 99% of the time.
If one of these don’t exist the person will not be able to gain muscle. Thus the person should stop worrying about gaining muscle and start fulfilling all of the prerequisites. Then gaining muscle will happen on its own.