Hi, I did the same thing with the same error. Below is my output.

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youtube-dl>youtube-dl -o file.mp4 https://120vod-adaptive.akamaized.net/exp=1614736952~acl=%2Fac5b90c6-5466-4e3c-a890-fae2579a867f%2F%2A~hmac=7a2ea7c275ac4b525491bb027615b0b3af7fcbd6d7d83a7cb794b2d8b35eb09b/ac5b90c6-5466-4e3c-a890-fae2579a867f/sep/video/9681a2af,be030397,1915f3ac,8c5dbfd6,7b647320.mpd

[generic] 9681a2af,be030397,1915f3ac,8c5dbfd6,7b647320: Requesting header

WARNING: Could not send HEAD request to https://120vod-adaptive.akamaized.net/exp=1614736952~acl=%2Fac5b90c6-5466-4e3c-a890-fae2579a867f%2F%2A~hmac=7a2ea7c275ac4b525491bb027615b0b3af7fcbd6d7d83a7cb794b2d8b35eb09b/ac5b90c6-5466-4e3c-a890-fae2579a867f/sep/video/9681a2af,be030397,1915f3ac,8c5dbfd6,7b647320.mpd: HTTP Error 404: Not Found

[generic] 9681a2af,be030397,1915f3ac,8c5dbfd6,7b647320: Downloading webpage

ERROR: Unable to download webpage: HTTP Error 404: Not Found (caused by HTTPError()); please report this issue on https://yt-dl.org/bug . Make sure you are using the latest version; type youtube-dl -U to update. Be sure to call youtube-dl with the --verbose flag and include its complete output.