I hope the author is well and Covid free. It has been so long since the last update.
Is it a plotline issue? Although the book has demonstrated Devotional Sex principles heretofore, there is very little story apart from the curmudgeonly, poor sap husband being dragged slowly into it.
Something else needs to intersect with the current thread. It could be Knight Lending or Princess Hotwifing, a breakdown in one or other of the relationships, a temporary or permanent change of partners, the formation of a poly foursome, or a different theme altogether.
You could of course rewrite it so that it leads with a main storyline in which they are: repo agents, paranormal investigators, TV researchers, documentary film makers, traffic wardens, hacked off teachers, ambulance drivers, research scientists, dog whisperers, relationship coaches, wedding planners, solicitors called 'Divorces R Us' or pest controllers.
Also, the characters could develop more. At the moment, it's frightfully PC. In the experienced couple, the Princess knows it all and hubby gratefully does as he's told. In the nubie couple, she's 'woke' and he's a small minded twat which is a bit clichéd. Is there any possibility of the women being anything less than perfect or of the men being anything more than twats? The story would then be more believable and more possibilities would arise.
Hope that helps.