Surkus members that signed up for an account prior to August 13, 2018, do not require a password. Simply sign back in by clicking "Continue with Facebook." If the app still prompts for login credentials, sign in using your Facebook login credentials.
For those who have a password, but can't remember it, you can always retrieve it by using the "forgot password" feature here - https://members.surkus.com/forgot-password.
Just enter the email address associated with your Surkus account and a link to set up a new password will be emailed to you.