I'd also go ahead and send a followup. At this point, you have nothing to lose in doing so. He could have had something come up in his personal life, been sick, etc. Or maybe he wanted to take time to reply in great detail but hasn't yet found uninterrupted time (with the pandemic, and my daughter and H being home all the time, it's more difficult for me to find time to get work done, for example). I would follow up and give him another chance to respond. Also, when is the session you booked?