Office 365 - Removing assigned License from Shared mailboxes using CSV

I am trying to remove Licenses from Shared Mailboxes using the following script:

$AccountSkuId = "Tenant:STANDARDWOFFPACK_IW_FACULTY"

$Users = Import-Csv "C:\mailbox.csv"

$Users | %{

 Set-MsolUserLicense -UserPrincipalName $_.UserPrincipalName  -RemoveLicenses $AccountSkuId

}

I get the following error:

"Set-MsolUserLicense : Unable to assign this license because it is invalid. Use the Get-MsolAccountSku cmdlet to
retrieve a list of valid licenses."

I absolutely know that the sku is correct.  I also closed and re-ran the PS session connecting to Exchange Online.  Any thoughts?