I was having this very same issue which for me, just started recently.
The fix for me was to add a “User-Agent” header to all my requests to the API. I had used the API since December 2019 without needing a user agent header so I’m not sure if something changed or if my client hit some kind of threshold.
More info at Cloudflare IM NOT A ROBOT blocking API?!? for anyone in the same situation.
Cheers! 