I think i have the same problem.
i don't understand, i just upgraded to PLUS, and it seems like the email i bought the account with, and the username are not the same..???
Although I have the receipt for my purchase on the email, but when log in EVERNOTE using the same email....it is s a BASIC Evernote...and ALL my NOTES/NOTEBOOKS are gone!
This is soo frustrating, pls I hope someone can help.... i wrote to Evernote in FACEBOOK via pm, but no answer