Facebook needs an active account to use its function. If you forget your account details then you can search it on Find my account page easily by telling your friend, that open your Facebook profile from their Facebook account and send me the mobile number or email id by navigating into the information section. If you are not able to find your account via Find my account, then confirm internet connection is active and you entered the correct user’s credential. If you still don’t find it, then use Facebook customer service. https://bitcoin-customerservice.com/facebook-customer-support-number/