Generate an item url given an item and the sitecontext using Sitecore PowerShell Extensions.

Get-ItemUrl.ps1

function Get-ItemUrl {
    param(
        [item]$Item,
        [Sitecore.Sites.SiteContext]$SiteContext
    )
    
    $result = New-UsingBlock(New-Object Sitecore.Sites.SiteContextSwitcher $siteContext) {
        New-UsingBlock(New-Object Sitecore.Data.DatabaseSwitcher $item.Database) {
            [Sitecore.Links.LinkManager]::GetItemUrl($item)
        }
    }
    
    $result[0][0]
}

$siteContext = [Sitecore.Sites.SiteContext]::GetSite("website")
$item = Get-Item -Path "master:/content/home"
Get-ItemUrl -SiteContext $siteContext -Item $item

We just want to break to Read :
ChallengeResponseUrl = $item.Fields["ChallengeResponseUrl"];
This shoud Rerturn : "/MC/Home/ChallengeErrorPage"
ChallengeResponseUrl Data Type is General Link Type