I figured it out for my account. The daily search quota was set to 0. I had to make a new project to get the default 10,000 quota. I'm not sure how this happened, but my API key for that project was created in 2018 and I don't think I ever used before so maybe Google set the quota to 0 due to inactivity. As soon as I got a project with the normal quota, videos started embedding correctly.
oh wow, this worked for me! that is so ridiculous from google but i can confirm making a new project rather than using an old one works
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Comment by @Kenkoman