Youtube-dl fails on youtube and works on other sites

I started having this issue a few days ago: youtube-dl no longer works for links to YouTube, but works fine for other sites such as Instagram:

$ youtube-dl https://www.instagram.com/p/B47c667AKPo/ 
[Instagram] B47c667AKPo: Downloading webpage
[download] Destination: Video by marieforleo-B47c667AKPo.mp4
[download]   2.5% of 40.44MiB at  1.45MiB/s ETA 00:27^C
...

$ youtube-dl https://www.youtube.com/watch?v=blHgexdxfVU 
Usage: youtube-dl [OPTIONS] URL [URL...]

youtube-dl: error: You must provide at least one URL.
Type youtube-dl --help to see a list of all options.

Ignoring HTTPS certificates with an HTTP address or [a --no-check-certificate](https://apple.stackexchange.com/questions/337958/error-downloading-youtube-video-using-youtube-dl) also fails. The same YouTube link and syntax worked a few weeks ago. I upgraded to the latest version, 2020.03.01, and still have the same issue. Is anything the matter between YouTube and youtube-dl?