Essence exchange is still bugged for me. Clicking on any option just results in "essence not found." I'm playing as futa, so maybe the issue is nb player characters aren't set up to give/receive essences?
The "Essence not found" message only occurs when the essence didn't get saved or saved improperly. In one of the recent patches I made some changes to how they were saved. Unfortunately, not all the fixes apply to essences that were obtained before the patch, so trying to use those essences may be resulting in the error for you.
Regardless of if that may be the case, I will continue looking into it. If these were obtained in the past week or so (assuming the game has been kept up to date), then any other information such as the type of essences attempted (Gender, Build, Identity, etc.), the essence details, (Male essence, Slim essence, Shoulder Length Hair essence) would help. Thank you for the report!