Please try the following to troubleshoot the issue:

• Check if the email address and password you entered are correct.
• Check if the email address you entered have been registered as a Synology Account. If not, please click here to register your email as a Synology Account.
• If you forgot your password, please reset it here. We recommend setting a simple test password to make sure you can sign in to Synology Account first, and then reset a safer password once the login is successful.
• Try clearing your browser's cache or disabling third-party software with password memory features. The wrong password may have been memorized and repeatedly entered, leading to the login failure.
• If you have enabled the two-step authentication for your Synology Account, make sure the verification code generated by the Synology Secure SignIn app (iOS/Android) is entered correctly before it expires.