When doing an import, you can get a "File corrupted" message. Even though the file is straight from the original logbook. Unfortunately this can happen sometimes, as some logbooks such as MCC Pilotlog, Crewlounge Pilotlog and some versions of LogTen Pro have crappy exporters and export corrupted data. Luckily there is something you can do about it.
Numbers or Excel
Load the CSV file in Numbers (on the Mac) or Excel (on a PC).
Here you can spot the corrupted rows quickly if you scroll through the data. When a certain row doesn't contain a date for example, you will know this is where it went wrong.
Just remove the corrupted rows, save/export the file as CSV again and retry the import.
Why it happens
The reason the files are corrupted, is because the logbook uses a delimiter such as ; to separate the fields. But if the remarks section for example also has this character, it will break the row on the wrong spot.
This could be solved by using enclosing character such as ". But the exports were not created using this, hence the issue with data corruption.
RB Logbook will detect this and will prevent the data from importing to protect against data corruption in the logbook itself.