i would say you are not installing it properly.
i think all that is needed is a language file and a payment module for a payment module to show up in the admin. they need to be in the right places.
without any log files, i am only venturing a guess. but plenty of store owners were able to get it to show up on the admin with nothing more than the directions that come with the module.
make sure you have not uploaded the for_upload directory.
best.
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