There is one question you must answer first: WHAT CHANGED? Your application may not have changed, but the environment in which it operates may have. Is there

There is one question you must answer first: WHAT CHANGED? Your application may not have changed, but the environment in which it operates may have. Is there a new alternative in that space? Don't limit your attention just to things that look exactly like yours: Consider everything that might conceivably be used instead of it. Or, are there new legal requirements which your product fails to satisfy? Or, did the legal requirement that necessitated the use of your product disappear? Also, given that this is recurring revenue, I am assuming you have a customer database, and you know who cancelled subscriptions. Do consider contacting a random sample of them and asking straight up if they would mind telling you why they stopped using it, and how they think you could improve the product to best serve their needs. Also, order of magnitude would be helpful here: Did 30 customers cancel? 300? 3,000? ... 30,000,000?