Nobody's accusing you of "responsibility" for anything. The HOA is asking for your cooperation in locating the leak.
You have no liability for an unforseen hidden leak, so cooperate and get it over with.
Might be inconvenient but that's what you get for living in a condo where every unit can affect every other unit.
Don't anticipate trouble until you actually have trouble.
Then come back and report.
Meantime, I can understand your reluctance to get your insurance company involved, but you are required by your policy to notify your claims department of any incident that may give rise to a claim, even if it ultimately doesn't. The claims people need an opportunity to investigate while it is possible to investigate. Your failure to comply with your policy is likely to give you more trouble later if you've prejudiced your company's right to investigate.