Building on this, if you don’t know at first but think you might, it’s ok to ask questions to flesh out and better understand the question. It highlights your troubleshooting skills. If you still don’t know and they tell you the answer, there’s nothing wrong with asking follow up questions. This can demonstrate your interest in the subject as well as possibly highlight knowledge they haven’t specifically asked you about.
In this vein, don’t forget that logs usually exist, and if they don’t you can often enable debugging. When something’s going wrong the first question I usually try to answer is “what’s the error message?” There isn’t always one, but if there is, knowing it can be a big help.
ETA: Most technical interviewers recognize that the average candidate will need some training for their specific environment, especially for junior positions. They’re looking for trainability, critical thinking, and troubleshooting skills. You may not be well versed in the specific tool they use for, e.g., configuration management, but if you demonstrate an understanding of the concept, that will show them that you can be easily trained to meet their specific needs.