EC2 Administrator has been expired - but cannot be changed

2 Options Via a SSM using Fleet Manager

1. Select the Node
2. Click Node Actions
3. Node Settings
4. Reset node user password
5. Enter Administrator and reset the password

Alternatively

Using SSM connect via Terminal to the Windows Instance.. You can run these PS commands to reset the password

$Password = Read-Host -AsSecureString
$UserAccount = Get-LocalUser -Name "Administrator"
$UserAccount | Set-LocalUser -Password $Password