Unable to login to a website via powershell - powershell

Question

I am trying to open a url in IE and then pass username and password to login to the url.But my code is not filling username and password
Following is code
$username = "userhere"
$password = "passhere"
$ie = New-Object -com InternetExplorer.Application
$ie.visible=$false
$ie.navigate("https://ameriprisestage.service-now.com/")
#while($ie.ReadyState -ne 4) {start-sleep -m 100}
$ie.document.getElementById("user_name").value= "$username"
$ie.document.getElementById("user_password").value = "$password"
Error: You cannot call a method on a null-valued expression. At line:7 char:1 + $ie.document.getElementById("user_name").value= "$username" + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : InvalidOperation: (:) [], RuntimeException + FullyQualifiedErrorId : InvokeMethodOnNull
You cannot call a method on a null-valued expression. At line:8 char:1 + $ie.document.getElementById("user_password").value = "$password" + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : InvalidOperation: (:) [], RuntimeException + FullyQualifiedErrorId : InvokeMethodOnNull

Answer 1

There is a couple of things to note. First, your page is not ready yet. Yuo must wait for load. Your commented line was intended to do that. Second, both fields are in iframe which works as a separate sandbox - has his own document object. I also removed window hiding code to see results. Here is working code:
$username = "userhere"
$password = "passhere"
$ie = New-Object -com InternetExplorer.Application
$ie.navigate("https://ameriprisestage.service-now.com/")
while($ie.ReadyState -ne 4) {start-sleep -m 100}
$ie.document.getElementById('gsft_main').contentWindow.document.getElementById('user_name').value = $username
$ie.document.getElementById('gsft_main').contentWindow.document.getElementById('user_password').value = $password
Make sure you close $ie object. You may have tons of them as background processes.