Useful when RDP won’t connect because NLA is an issue, or domain trust issues are present. If the remote OS is still accessible via PowerShell and your current user is also an administrator on the remote OS, try:
$ComputerName = "remotehostname"
(Get-WmiObject -class Win32_TSGeneralSetting -Namespace root\cimv2\terminalservices -ComputerName $ComputerName -Filter "TerminalName='RDP-tcp'").SetUserAuthenticationRequired(0)
Change the 0 to a 1 to re-enable.