Ok, but a completely fair and honest answer is to google it. Or review internal documentation/asbuilt for the system. Or to ask your mate steve.
You don't need to understand the technical detail in the hypothetical, to extract search terms and research it.
The answer of "I dont know that system so I wouldnt know where to start" is failing the hypothetical. You have many starting points for all technical research. It means you cannot even imagine where to begin.
If you are so shocked by the appearance of technical term you don't understand, that you wont even take the first step of putting that term into google, you really shouldn't be applying for technical jobs.
The most common answer I get, if I fight the interviewee, and reposition it as a technical issue they do understand, is that they relay to me an anecdote from a time when they did complete the troubleshooting. IE, they still dont engage with the hypothetical, they just use recall.