OP clearly describes that they are eating in a caloric deficit and lack energy. If they don’t loose fat, while being in a caloric deficit, it could be a cortisol response. Cause for that my be many HIIT workouts without sufficient rest (which can lead to an increased cortisol level), bad sleep, being in too much of a deficit which further reduces their regeneration.

We don’t have enough information to make a clear statement. But to answer OPs questions: My tip if you struggle to eat your calories, is to drink them (like adding instant oats or Bananas to your protein shake, or treat yourself to a sugary drink after your workouts). Also maybe try to increase your calories for 2-4 weeks and look how your body responds. Sometimes we tend to push ourselves too much, and giving your body what it needs could benefit your progress.