[Ripplinger]

Did all that, even removed the newer books from the device and resent them, and still having the same issue. I also tried reading older books that were on the reader and now they also won't appear on the homepage after opening them and reading for a bit.

I've got another spare reader I'll test sending it to from my old and untouched Calibre 4.23 that's still on another PC with Windows 10 and see what happens. The main Kobo GloHD I'm reading from hasn't been connected at all since I did all these upgrades, I tried it on a spare reader first. Yes, I have 3 spares, I love the GloHD that much I have no intention of ever giving it up.

Edit: Btw, I am using Calibre 8.11.1, I did have the updated version.