@NightStar76: Some suggestions are above, but, here is the list of things to try. This is basically in order of ease:
- Check the date and time on the device. It should be synced, but, if it is to far out for some reason, this can fail. And then cause other issues.
- Restart the device.
- Remove the WiFi, restart and connect again.
- Check the database. If you are a calibre user, then my Kobo Utilities plugin is the simplest way to do this. Otherwise, any SQLite database manager will let you do it.
- Use the account repair function. This is on the Device information page of the settings.
- Manually reinstall the current firmware. This should help, but, it occasionally does.
- Sign out of the Kobo account. This will clean up the database, generate a new one and start downloading the books again. Unfortunately, this clears all information about the sideloaded books and then reimports them.
- Do a factory reset from the Device information page of the settings. This wipes the books partition and does the setup again. (Note: Personally, I skip this and use the next method.)
- Do a manual factory reset or enable developer mode and do it from that page. This is more thorough than the above as it also wipes root partition and then installs the factory firmware.
The other possibility is external to the device. If your connection to the internet has issues, it can cause this sort of problem. This happened to me for some time. My ADSL service was a bit flaky. Sometimes the sync to minutes, other times it was unending. When that happened, I could prove connectivity issues. Clearing them up and restarting the sync would solve it. I don't have this problem now as my internet is completely different and very reliable.