Hmm, but it says that Microsoft Project files are supported, but I cannot see aspose-tasks on the dependency list:
Do you have some file that is problematic to open with the GroupDocs.Annotation for Java? Please, attach it to the forum post, so we can examine it.
I don’t have a sample file, but I have problem with finding all the required dependencies. You guide me to that mentioned URL which doesn’t contains aspose-tasks dependency which means that mpp files will not work. So it looks like more question of required dependencies?