You could use audit logs to check who and when view the video.
1.You should have one of following admin role to use audit logs.
2.Sign into the Microsoft Purview compliance portal -> Select the Audit tab on the left panel of the homepage to navigate to the Audit tool -> Select New Search tab at the top of the Audit page -> Set Data and time range -> Choose Accessed file in the actives -> Enter file URL in the File, folder, or site -> Then search audit logs.
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