Bro, you have a typo trree instead of tree. I'm sure that's why it gives the error.
Try to write the correct name for maple. Here is an example of the fix: Registry.register(BuiltinRegistries.CONFIGURED_FEATURE, new Identifier("japan_mod", "trree"), CUSTOM_TREE);
If your maple still doesn't grow after this, check your world settings and make sure it loads the mod correctly.