...
If the VAT organisation number is invalid or doesn’t exist, this message will appear:
...
Sending documents to Swedish or Danish recipients
It is possible to send documents to Swedish and Danish recipients, though currently our app does not have any look-up functionality, if you know the recipient is registered as a PEPPOL recipient you can send to them.
You can use this tool to check if your recipient is applicable: Peppol Directory - Search
How to send PEPPOL document
...