Downloading Reflexil binaries from the official repository does not work for JustDecompile since the actual JustDecompile plugin is missing there. It's only core Reflexil functionality you download.
The first and recommended way of getting the JustDecompile plugins is thought the plugin manager.
The second one is to download the source code for the JustDecompile plugins from the official plugins repository
and to build it. Then you can get the binaries from the output folder.
The third way is to copy the plugin folder from JustDecompile with already installed plugins.
Based on your post and on the screenshots I assume that you must install JustDecompile on offline machine. If this is the case, at the moment you should use the third option. As I said the second one will be available soon.
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