What this is about
The buyer reference is filled but does not match the structure of a Leitweg-ID. For invoices to authorities that is almost always an error; for business customers other content is allowed.
What to do
If the recipient is a public authority, check the routing ID.
Does the error keep coming back?
Then it is not chance but a pipe connected the wrong way. The free 15-minute check finds the spot.
Arrange a check