You need to either add this header:
'Referrer-Policy': 'strict-origin-when-cross-origin'

Or you can add the following to your embed element:
referrerpolicy='strict-origin-when-cross-origin'

Either should work for you to get them back up and running.

See YouTube documentation here:
https://developers.google.com/youtube/terms/required-minimum-functionality#embedded-player-api-client-identity