As per France documentation on JournalCode from FEC report :

"the journal code refers to the coding used in accounting software to reference the different journals. These codes can consist of numbers, letters, or a combination of both."

Currently in Dynamics we only implemented the us of letters. If the Journal Code is defined in the Number sequence to include Numbers or Letter+Numbers it will report Blank or only the Letter part on the FEC report.

Request is to allow using numbers or combination of numbers and letters as mentioned in the France documentation: https://bofip.impots.gouv.fr/bofip/9028-PGP.html/identifiant%3DBOI-CF-IOR-60-40-20-20170607