Writing new lines to a text file in PowerShell

`n is a line feed character. Notepad (prior to Windows 10) expects linebreaks to be encoded as `r`n (carriage return + line feed, CR-LF). Open the file in some useful editor (SciTE, Notepad++, UltraEdit-32, Vim, ...) and convert the linebreaks to CR-LF. Or use PowerShell:

(Get-Content $logpath | Out-String) -replace "`n", "`r`n" | Out-File $logpath

You can use the Environment class's static NewLine property to get the proper newline:

$errorMsg =  "{0} Error {1}{2} key {3} expected: {4}{5} local value is: {6}" -f `
               (Get-Date),$keyPath,$value,$key,$policyValue,([Environment]::NewLine),$localValue
Add-Content -Path $logpath $errorMsg

It's also possible to assign newline and carriage return to variables and then append them to texts inside PowerShell scripts:

$OFS = "`r`n"
$msg = "This is First Line" + $OFS + "This is Second Line" + $OFS
Write-Host $msg