I tried logging out of the mac client, and then logging into web. I still got the same error about the username not existing.
I logged back into the mac client and then going to devices. I can see that a web client already is connected, so I revoked access. Then tried to login in again and still I got the error about the account not existing for email address.
Now devices no longer has web client in it. So, I now log out of the mac client, when I check devices there are no devices listed. I try to login again and still get the message about the account not existing for email address.
I can successfully sign back into the mac client.
To me it looks like a problem with the web login page not being able to find my account. I can access all areas of web if I use the mac client. My mac client works fine. I just can't access evernote on web via the web login page.
Note that I created my account via the mac client.