Due to a change in the naming format of language folders from Maxon Cinema4D R19 to R20, Zoom Cinema4D plugin users need to update the names language folders for the plugin to pick up the correct language strings.
Up until R19, the naming format for localization folders only used a language code, like strings_en or strings_de.
From R20 onwards, the naming format for the localization folders has changed to use language code with locale code, like strings_en-us or strings_de-de. You need to manually rename the folders for the correct language strings to be picked up for the plugin.