There are many great sales methodologies out there, SPIN, Miller Heiman, EDGE framework and others. No matter which dogma you choose, they all have one common weakness, as good as they look on the page, they all need to be executed to matter.
There is no getting away from the fact that the biggest reason for a lack of sales is a lack of execution. The sad truth is that sales people know what they have to do, they just don’t do it. You can train them, but can’t make them. It’s the age old “doer and the thinker”, in sales the doer executes and wins. There are many great plans gathering dust on shelves, but the winning plans are the ones actually executed.