SQL Azure – The ImportExport operation failed because of invalid storage credentials

When I run my script below it keeps failing with "The ImportExport operation failed because of invalid storage credentials."
The access key and SAS all seem to be correct when I check in the portal. Can someone please point me in the right direction

    param(
        [string]$SubscriptionId,
        [string]$ResourceGroupName,
        [string]$storageRG,
        [string]$ServerName,
        [string]$DatabaseName,
        [string]$StorageAccountName,
        [string]$StorageContainerName,
        [string]$StorageAccountKey,
        [string]$ImportBacpacFilename,
        [string]$AdministratorLogin, 
        [string]$AdministratorLoginPassword
    )

    Add-Type -AssemblyName System.Web

    try {
        # Set the subscription context
        Write-Verbose "Setting subscription context..."
        Select-AzSubscription -SubscriptionId $SubscriptionId

        # Get the storage account
        Write-Verbose "Getting storage account..."
        $StorageAccount = Get-AzStorageAccount -ResourceGroupName $storageRG -Name $StorageAccountName

        # Get the storage account context
        Write-Verbose "Getting storage account context..."
        $StorageAccountContext = $StorageAccount.Context

        # Generate the SAS token for the storage container
        $StartTime = Get-Date
        $ExpiryTime = $StartTime.AddHours(6)
        $SasTokenRaw = New-AzStorageContainerSASToken -Name $StorageContainerName -Permission rw -StartTime $StartTime -ExpiryTime $ExpiryTime -Context $StorageAccountContext
        $SasToken = [System.Web.HttpUtility]::UrlEncode($SasTokenRaw)
        $StorageAccountKey = (Get-AzStorageAccountKey -ResourceGroupName $storageRG -Name $StorageAccountName)[0].Value
        # Build the destination URL
        $Sourceurl = "https://$StorageAccountName.blob.core.windows.net/$StorageContainerName/$ImportBacpacFilename$SasToken"
        # Import the Azure SQL Database to the Blob Storage container
        $ImportRequest = New-AzSqlDatabaseImport -DatabaseName $DatabaseName -ResourceGroupName $ResourceGroupName -StorageKeyType StorageAccessKey -StorageKey $StorageAccountKey -StorageUri $Sourceurl -Edition Standard -ServiceObjectiveName S0 -DatabaseMaxSizeBytes 5000000 -AdministratorLogin $AdministratorLogin -AdministratorLoginPassword (ConvertTo-SecureString $AdministratorLoginPassword -AsPlainText -Force)-ServerName $ServerName

        # Check the status of the import operation
        $ImportStatus = Get-AzSqlDatabaseImportExportStatus -OperationStatusLink $ImportRequest.OperationStatusLink
        [System.Console]::Write("Importing")
        while ($ImportStatus.Status -eq "InProgress") {
            Start-Sleep -s 30
            $ImportStatus = Get-AzSqlDatabaseImportExportStatus -OperationStatusLink $ImportStatus.OperationStatusLink
            [System.Console]::Write(".")
        }
        [System.Console]::Write("")
        $ImportStatus
        if ($ImportStatus.Status -eq "Succeeded") {
            Write-Host "Import completed successfully!"
        }
        else {
            Write-Host "Import failed. Status: $($ImportStatus.Status)"
        }
    }
    catch {
        Write-Error "An error occurred: $_"
    }

}