Here is another way using WebRequest, I hope it will work for you
$user = 'whatever'
$pass = 'whatever'
$secpasswd = ConvertTo-SecureString $pass -AsPlainText -Force
$credential = New-Object System.Management.Automation.PSCredential($user, $secpasswd)
$headers = @{ Authorization = "Basic Zm9vOmJhcg==" }
Invoke-WebRequest -Credential $credential -Headers $headers -Uri "https://dc01.test.local/"