Important iOS 10.1 has been released, I'm in the process of verrifying that this fixes the issue. I will update here when confirmed.
If you are having an issue where the default notification sound plays instead of the Lotus Bud bell, you are not alone. In iOS 10 Apple has introduced a bug that is causing this. I have filed a bug with Apple, I have to wait for the fix from Apple to resolve.
I apologize for the annoyance. I'm sorry that I don't have the ability to fix it. Hopefully Apple will release an update that will resolve the problem. I will post back here once I have confirmed that Apple has resolved the issue.