youtube-dl: [youtube] Unable to download age-gated videos.

Checklist

• I’m reporting a broken site support
• I’ve verified that I’m running youtube-dl version 2021.03.14
• I’ve checked that all provided URLs are alive and playable in a browser
• I’ve checked that all URLs and arguments with special characters are properly quoted or escaped
• I’ve searched the bugtracker for similar issues including closed ones

Verbose log

non Cookies set.

C:\Users\PC\Downloads>youtube-dl iMJ6BNYipv0 -v
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: ['iMJ6BNYipv0', '-v']
[debug] Encodings: locale cp949, fs utf-8, out utf-8, pref cp949
[debug] youtube-dl version 2021.03.14
[debug] Python version 3.9.2 (CPython) - Windows-10-10.0.19041-SP0
[debug] exe versions: ffmpeg 4.3.1, ffprobe 4.3.1
[debug] Proxy map: {}
[youtube] iMJ6BNYipv0: Downloading webpage
[youtube] iMJ6BNYipv0: Refetching age-gated info webpage
ERROR: Sign in to confirm your age
This video may be inappropriate for some users.
Traceback (most recent call last):
  File "c:\private\python3.9.2\lib\site-packages\youtube_dl\YoutubeDL.py", line 806, in wrapper
    return func(self, *args, **kwargs)
  File "c:\private\python3.9.2\lib\site-packages\youtube_dl\YoutubeDL.py", line 827, in __extract_info
    ie_result = ie.extract(url)
  File "c:\private\python3.9.2\lib\site-packages\youtube_dl\extractor\common.py", line 534, in extract
    ie_result = self._real_extract(url)
  File "c:\private\python3.9.2\lib\site-packages\youtube_dl\extractor\youtube.py", line 1658, in _real_extract
    raise ExtractorError(reason, expected=True)
youtube_dl.utils.ExtractorError: Sign in to confirm your age
This video may be inappropriate for some users.

Cookies set.

C:\Users\PC\Downloads>youtube-dl --cookies cookies.txt iMJ6BNYipv0 -v
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: ['--cookies', 'cookies.txt', 'iMJ6BNYipv0', '-v']
[debug] Encodings: locale cp949, fs utf-8, out utf-8, pref cp949
[debug] youtube-dl version 2021.03.14
[debug] Python version 3.9.2 (CPython) - Windows-10-10.0.19041-SP0
[debug] exe versions: ffmpeg 4.3.1, ffprobe 4.3.1
[debug] Proxy map: {}
[youtube] iMJ6BNYipv0: Downloading webpage
ERROR: This video may be inappropriate for some users.
Traceback (most recent call last):
  File "c:\private\python3.9.2\lib\site-packages\youtube_dl\YoutubeDL.py", line 806, in wrapper
    return func(self, *args, **kwargs)
  File "c:\private\python3.9.2\lib\site-packages\youtube_dl\YoutubeDL.py", line 827, in __extract_info
    ie_result = ie.extract(url)
  File "c:\private\python3.9.2\lib\site-packages\youtube_dl\extractor\common.py", line 534, in extract
    ie_result = self._real_extract(url)
  File "c:\private\python3.9.2\lib\site-packages\youtube_dl\extractor\youtube.py", line 1658, in _real_extract
    raise ExtractorError(reason, expected=True)
youtube_dl.utils.ExtractorError: This video may be inappropriate for some users.

Description

If set cookies or not, will get this error.