I'm having a similar issue. I paid for premium, and I have a receipt from both Evernote and Apple proving I paid. For a couple of days after the purchase, everywhere I log into Evernote said I have a plus subscription. Now my plus subscription has expired, and when I log into Evernote it shows me as having a basic account.
Also, I tried to click "Restore My Purchases" as it recommends here https://help.evernote.com/hc/en-us/articles/209004677-I-purchased-an-Evernote-subscription-through-iTunes-but-my-account-is-still-Basic, but that button is gone.