My 2c/3a hair was feeling a bit dry after Hennaing about a week later, so I did a deep treatment that I realized later was protein rich.. after leaving it on only slightly longer than recommended, I washed it out and put some coconut oil on wet hair and slept on that.. I then washed that out and dried it with a diffuser.. the result was fabulous curl formation BUT flat flat flat!.. does this mean my hair doesn't like protein or that I didn't need the deep conditioner.. or what? It also felt very thin.. where as usually it feels much much fuller..
Usually protein sensitivity results in hard, crispy, dry, rough or matted feeling hair. No expert by any means just my experience with some protein sensitivity and what I've read about. It may have been the deep moisturizing that caused the cuticle to lay really flat and was a bit heavy for your hair. My guess is that once you wash it again it will have more volume.