I'm asking for details because you are obviously doing something wrong. You haven't even mentioned what's not working exactly. "Merging" can mean a lot of things, e.g. simply muxing as additional track. You have to use appending. You can also not simply use the original chapters, they have to be edited. Depending on the files a simple append might also break playback and require re-encoding.
What release are we talking about anyway?
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