Getting InvokeMethodOnNull when the object exists

gistfile1.txt

$texPasswordFile = "C:\users\$env:username\website.txt" 
$tsPasswordFile = "C:\users\$env:username\website2.txt"
$texLoginFields = @("txtUser", "txtPassword", "Login", "username")
$tsLoginFields = @("test", "test")
$telestaff = "https://www.telestaff.net/servlet/ServletController?device=stdbrowser&action=doBeginLogin"
$texcom = "https://www.texcom.com/login.php"
 
# Function to return a password from an encrypted file, or store it if file not found 
Function get-password($credentialsfile) 
{ 
    #Check to see if the file exists 
    if (-not (Test-Path $credentialsfile))
        { 
        #If not, then prompt user for the credential 
        $creds = Get-Credential 
        #Get the password part 
        $encpassword = $creds.password 
        # Convert it from secure string and save it to the specified file 
        $encpassword |ConvertFrom-SecureString |Set-Content $credentialsfile
        Remove-Item $creds
        } 
    else 
        { 
        #If the file exists, get the content and convert it back to secure string 
        $encpassword = get-content $credentialsfile | convertto-securestring 
        } 
    # Use the Marshal classes to create a pointer to the secure string in memory 
    $ptr = [System.Runtime.InteropServices.Marshal]::SecureStringToCoTaskMemUnicode($encpassword) 
    # Change the value at the pointer back to unicode (i.e. plaintext) 
    $pass = [System.Runtime.InteropServices.Marshal]::PtrToStringUni($ptr) 
    # Clear the pointer and the secure string
    [System.Runtime.InteropServices.Marshal]::ZeroFreeCoTaskMemUnicode($ptr)
    $encpassword.Dispose()
    remove-variable encpassword,ptr 
    # Return the decrypted password 
    return $pass 
}

#Function to launch IE and login to a site: returns the IE object so it can be interacted with later 
Function Start-IE($startSite) 
{
    $ie = New-Object -com InternetExplorer.Application
    $ie.Navigate($startSite)
    $ie.Visible = $true
    #wait for page to load
    while ($ie.Busy) 
    {
        start-sleep -s 1
    }
    login-website $startSite $ie
    Return $ie
}

#Function to log in to site (use "show source" to locate element IDs and customize for each site)
#If additional sites are desired will likely need to add separate cases for each site
#credit to https://www.sepago.com/blog/2016/05/03/powershell-exception-0x800a01b6-while-using-getelementsbytagname-getelementsbyname
Function login-website($loginSite, $ieobj)
{
    switch ($loginSite)
    {
        $texcom
        {
            $user = $ieobj.document.IHTMLDocument3_getElementByID($texLoginFields[0])
            $user.value = $texLoginFields[3]
            $pwd = $ieobj.document.IHTMLDocument3_getElementByID($texLoginFields[1])
            $pwd.value = (get-password $texPasswordFile)
            $login = $ieobj.document.IHTMLDocument3_getElementByID($texLoginFields[2])
            $login.click()
        }
        $telestaff
        {
            $fields = $ieobj.document.IHTMLDocument3_getElementsByTagName("INPUT")
            $fields[2].value = $tsLoginFields[0]
            $fields[3].value = (get-password $tsPasswordFile)
            $fields[4].value = $tsLoginFields[1]
            $fields[5].click()
            #write-host $fields
        }
        default
        {
            Write-Debug("no supported website submitted to function")
        }
    }
}


#Function to test for login page and redo login if necessary
#note: if not on login page, the active page will be reloaded to hopefully maintain session activity
function test-logonPage($ieObjToTest)
{
    switch ($ieObjToTest.LocationURL)
    { 
        <#$texcom
        {
            login-website $texcom, $ieObjToTest
        }
        $telestaff
        {
            login-website $telestaff, $ieObjToTest
        }#>
        default
        {
            $ieObjToTest.Refresh()
        }
    }    
}

#Launch websites  
$ieTex = Start-IE $texcom
$ieTS = Start-IE $telestaff




#reload page after 1 minute

    Start-Sleep -s 60
    test-logonPage $ieTex
    test-logonPage $ieTS