(I only have a Libra 2 so take this with salt)
There should be 2 files in the
root folder of the Kobo with 'calibre' as part of their name.
These identify that a (specific) Calibre PC has inventoried and indexed the books. If you delete, then the indexing process must start over. best wait for instructions before deleting.
Also note that if you did anything in Calibre that changed the title, series name or Author. There may be a newer version using that on the device, so no
Match
Also, if you had a older Calibre (like 6 or 7) and did a big jump. There were driver changes and the default path changed. I had to
fix mine to include 'MyBooks/'
Code:
MyBooks/{series}/{series_index:0>2s}-{title}-{authors}
FWIW Calibre finds the books, but sending again results in (2 books) in the tick column