Hi,
As you know, the tax code is determining from the consignment info record. Please cross check whether any changes has been happened in the consignment info record and tax code still exists in consignment info record. Also cross check whether the info record is flagged for deletion in ME15. If it exists, active, and still MRKO is throwing the same message, cross check the points mentioned in the note: 87860 - Consignment: determining tax code as of 4.0
Regards,
AKPT