Downloading subtitles from Pluralsight does not work

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If the purpose of this issue is a bug report, site support request or you are not completely sure provide the full verbose output as follows:

Add the -v flag to your command line you run youtube-dl with (youtube-dl -v <your command line>), copy the whole output and insert it here. It should look similar to one below (replace it with your log inserted between triple ```):

[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: ['--username', 'PRIVATE', '--password', 'PRIVATE', '--verbose', '-o', '%(playlist_index)s_%(playlist)s_%(title)s.%(ext)s', '--all-subs', '--sub-format', 'srt', '--write-sub', '--sleep-interval', '120', 'https://app.pluralsight.com/library/courses/mvc4', '--skip-download']
[debug] Encodings: locale cp1250, fs mbcs, out cp852, pref cp1250
[debug] youtube-dl version 2018.09.26
[debug] Python version 3.4.4 (CPython) - Windows-10-10.0.17134
[debug] exe versions: none
[debug] Proxy map: {}
...
<end of log>

Description of your issue, suggested solution and other information

I can't download subtitles from pluralsight. I saw previous issue (#9681) on bugtracker, but it was closed.
Here's sample output from youtube-dl:
[download] Downloading video 10 of 52
[pluralsight] mvc4-m2-introduction-ii-3: Downloading JSON metadata
[pluralsight] mvc4-m2-introduction-ii-3: Downloading mp4-high viewclip graphql
[pluralsight] mvc4-m2-introduction-ii-3: Waiting for 2 seconds to avoid throttling
[pluralsight] mvc4-m2-introduction-ii-3: Downloading captions JSON
WARNING: Unable to download captions JSON: HTTP Error 404: Not Found

I've checked other playlists and other command line options like:
--all-subs
--write-sub

Always get the same error: "WARNING: Unable to download captions JSON: HTTP Error 404: Not Found"