Face Index Deletion Causing Enrollment Error 21

I have deleted all the face indexes from my app.

Failed deleting efbd0b4ca6bf40b88a91c3ee70fcec64fioa4e0c: {"status":404,"error":"Empty Application Index. Please enroll your first user before performing this API call."}

but now when trying to enroll it errors out with code 21... why is that if the face is destroyed?