I honestly don’t know what’s up at Evernote. They definitely made some changes lately regarding the API. I was not aware of the rate limit change, but was able to reproduce it here without an excessive amount of use.
They also recently changed some of how they are handling HTML entities in a way that messes with some of Drafts actions.
But there have been no announcements that I have seen about these changes, and they have no way to contact developer support (have not in years)…so I’m unlikely to get an answer from them if I asked.
I’ve been expecting this Evernote integration to stop working at any time for years, I recommend if you switch to email based actions as discussed in the integration guide.