Hello Shane,
Thank you for your question and for reaching out with your question today.
This is happening because the remembered username is not including the domain. Therefore, it will not authenticate and when entered manually, it will. In order to resolve this issue you need to ensure that Windows 10 remembers not only the username, but also the domain to which it is connecting.
- Type gpedit.msc into Run box, Enter.
- Navigate to the following group policy object:
Computer Configuration\Administrative Templates\System\Logon
- Find the entry "Block user from showing account details on sign-in" and "Do not enumerate connected users on domain-joined computer" and "Enumerate local users on domain-joined computers" in the right pane.
- Configure "Block user from showing account details on sign-in" and "Do not enumerate connected users on domain-joined computer" as "Not configured" or "Disabled".
- If you want to list all local user account, you can set "Enumerate local users on domain-joined computers" policy as "Enabled".
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Best regards.