If you registered by clicking Continue with Apple and you opted to hide your login, your account may be associated with an email address ending in privaterelay.appleid.com.
To view the email address Apple generated for you, please go to https://account.grammarly.com/. This email address is linked to your Apple ID.
To log in to your Grammarly account, please click Continue with Apple at https://www.grammarly.com/signin or in your preferred Grammarly product.