You can only upload the files to the FTP server that were agreed upon with HRinstruments, and then import them. The files are automatically copied from there to the import directory at agreed times (via a so-called cronjob) and then imported by another cronjob. If you want to change the import, it is recommended to test the changes via the Manual Data Import (=GUI) before editing the file. In the GUI you will be shown any errors in the uploaded file.
The import via the GUI is more strict than the import via the Automated User Synchronisation (=API), so that the users know which data is wrong or missing. In case of an API, the departments can be formed dynamically from the value in the “Department” column of the LOP (see Data Import). This workaround only works via the API, not when importing data manually. If your goal is to use the import via the GUI only to check the data, you can ignore this error. If your goal is to actually perform the import via the GUI, you have to manually create the missing departments from the lines mentioned in the error message beforehand, or import them using the LOS file (see Data Import).