Hi @Jay-10-yao,
Thank you for your report. Could you please confirm if you defeated the SENTINEL minion while at full health?
If you did, the reason you didn’t heal is that the Response ability triggers before any consequential damage occurs.
If you did not, could you please share your save file? This will help us determine which minion you defeated and what cards were in play at that time.
Let me know if you have any further questions!