Hi, CTO and co-founder of Cronofy here.
Around 12 hours ago our Evernote connector started seeing more errors than normal when communicating with Evernote's API. Specifically a type of "unauthorized" response we have not seen before.
We are now treating this the same as our authorization to Evernote for your account being invalidated and so will be asking you to relink. However, it appears the authorization process has also changed because that is not completing successfully, resulting in the error shared here.
We are investigating the issue and are going to be in touch with Evernote to understand what has happened. Our integration has not been altered in a meaningful way for nearly a year and we've not seen, nor found, any notifications about the API changing so there's not anything obvious for us to do to resolve the problem at this point.