Why do my watched videos not appear in my YouTube watch history?

Hyper stores watched videos locally in the "Device" watch history.
You can view your YouTube account watch history, however videos you watch in Hyper will not be added to this history. 
Sadly, there is no official way to add videos to the account watch history or sync the account and Device history.
This is a limitation of the provided YouTube API and most likely has to do with protecting YouTube videos from "view spoofing".

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