Why has my client with back pain not improved following the two sessions of Deep Subconscious Channeling with Trauma Resolution?

This simply requires more time for the benefits to manifest. The healing has been set in motion through dealing with the many events on other timelines that are intertwined now to conspire and bring about energetic discord within the body—felt as discomfort. He has experienced turnarounds previously and enjoys a current much reduced pain level. What is remaining is the minor component. So the lack of an immediate benefit is not evidence the session was ineffective, only that an outcome desired was not immediately apparent. Give this more time and you will see things change for the better without further work being done.