Kobo Clare 2E : Problem with Collections and series.

Hello,

I have a new problem while transferring books to my Kobo.

Collections/series are no longer created, nor are new books added to the existing collections and series.

The problem might have started when a replaced my pc, but the library was untouched as it sits on a NAS.

My config is as follows :
Collections columns : #series
Collections template : empty
Create collections : checked
Delete empty collections : checked

Thanks for any suggestions