Update VA Powershell

Guys. 

I am trying to update a VA with the value from a CSV file. 

Attribute1 is a DirectoryString VA. I have similar code that's works fine if the attribute is a BOOLEAN but trying to set this on a DirectoryString fails. 

#Set Runtime Parameters
$CSVImport = "C:\CSVFILE.csv"

Connect-QADService -Service "ARS-SERVER-Name" -Proxy
Import-Csv $CSVImport | ForEach-Object {
Set-QADUser -IncludedProperties 'Attribute1' -Identity $_.UserName -ObjectAttributes @{"Attribute1"=" $_.Url"}
}