Yes, both the invoice supplying organisation and the invoice receiving organisation need to be on LUCA+.
LUCA+ requires access to both supplier and customer accounting solutions in order to capture and synchronise invoices between accounting software. If the supplying organisation is not using LUCA+, invoices cannot be pulled from their accounting solution when an invoice is sent. Make sure the supplying organisation is using LUCA+ and try again.
To invite others to use automatic invoice processing (e-invoicing), see Inviting others to LUCA+