I have been using Calibre (on my Macbook) with Kobo e-readers for 2 years now.
I got a Kobo Aura last year, and it has been working fine until now. I reset my Kobo aura (because I had inadvertedly created 2 libraries in Calibre and I didn't know in which library each ebook was) and re-uploaded all my ebooks (300+ epubs) into the main memory using Calibre (in Calibre, all of them are ticked as imported into the device) but only 23 are actually displayed in the Kobo library. I have read several similar issues on various Kobo devices and have tried the different solutions but they don't work for me.
I use Calibre 2.41 and the latest Kobo firmware (3.18.0)

please!