By default, payments can go only to addresses saved as counterparties. If you need to pay a one-off address, you can enable Allow payments to unsaved addresses in Settings → General → Payments (it applies to your account and needs a confirmation code).
Once it's on, when you create a payment you can type an address straight into the wallet field and choose Pay to this address. The payment is sent to that address without saving it to your address book.
If an imported or typed address isn't linked to any counterparty and this setting is off, that row stays blocked and the batch can't be sent until you enable the setting or add the counterparty. Because crypto transfers can't be reversed, double-check every unsaved address before you send.