The curse of knowledge is a cognitive bias that occurs when an individual, communicating with other individuals, unknowingly assumes that the others have the background to understand. (Wikipedia)
We assume everyone has the same level of knowledge. When they don’t get what you are explaining, we believe either something wrong with them or us.
Especially, we experience this when you are onboarding a new feature for users or customers. We are assuming they will choose whatever paths we designed for them.
I think before doing anything else, you should start to ask questions from basic to advance in order to understand their background.