If soundbank loading or playback of a streamed file fails, the first step is to connect the Wwise tool to your game, start a capture, and look for error notifications (in yellow).
If the error "Cannot find file" is displayed, it means that Wwise was not able to locate the specified file. File location is resolved by the game, in its implementation of AK::StreamMgr::IAkFileLocationResolver::Open(). All games need to implement this interface and register it to the Stream Manager. Your game might be using the default low-level I/O samples that are distributed with the SDK (in samples/SoundEngine/).
The most straightforward way to debug this is to set a breakpoint into your implementation of AK::StreamMgr::IAkFileLocationResolver::Open() (both overloads), step into the code and see why file opening failed. Most of the time, it is simply because a path is not set correctly somewhere.
One subset of the low-level I/O samples uses the file location base services (CAkFileLocationBase). This class is very simple: it exposes a function called "SetBasePath()", and prepends all file names with the string that was passed to this function. Search for this function in your code, and see if you passed the correct path.
Another subset of the low-level I/O samples uses file packages. Ensure that you properly generated your package(s) and loaded them using CAkFilePackageLowLevelIO::LoadFilePackage().
If the problem occurs only with streamed files, ensure that the streamed files are correctly deployed. Usually, you need to either copy them, or package them along with soundbanks, in a post-soundbank-generation step. Refer to the SDK documentation and the Wwise Help in the Soundbank Settings dialog for more details about this.
