There might be a mismatch between the email address that you subscribed with in the landing page and the email address that you created your account with in the app.
Please check the Boards app to make sure you created your account with the same email address by opening the app and tapping "Account".
Then, check the email address on the screen. If it's the same, it means that the mistake was made when registering on the landing page, and you need to register again.