If you are having issues signing in to the Mylio Photos application, Account Management Page, or resetting your password and get an error that starts with 15810… then your Mylio Photos account was most likely created using a third-party sign-in option (Apple, Google, Facebook, or Microsoft).
If you're already signed in to the Mylio Photos application on a device, you can check how your account was created by opening the Account menu (the person icon in the top-right). If your account was created with a third-party login, it will say so at the top. If you are signed in with an email address, your email will be listed. If you are still unsure about how or why you are receiving a sign-in error, feel free to Contact Support for assistance.