Start here.
Start by identifying what failed: delivery, opening, reading position, or highlights. Then identify the source and reader. Do not reset the device or replace files before preserving your reading context.
Record the symptom precisely
Write down what changed, when it last worked, and whether one book or all books are affected. A single replaced EPUB points to a different cause than every title failing after an account change.
Verify the expected behavior
A sideloaded file does not automatically inherit every account feature of a store purchase. Confirm that your chosen route actually supports the missing layer of sync. Otherwise troubleshoot the workflow, not the device.
Change one thing at a time
Test a known small EPUB without annotations, then compare the failing book. Keep originals and notes safe. Avoid broad resets until a supported troubleshooting route specifically requires them.
The details, at a glance.
| Consider | What to look for |
|---|---|
| Book missing | Check delivery and library import |
| Book will not open | Inspect the file and reader support |
| Position missing | Check reading-state route and edition |
| Highlights missing | Check annotation support and export |
A few things worth asking.
Should I factory-reset first?
No. Preserve data and identify the failing layer before considering a destructive troubleshooting step.
Why does a store book work but my EPUB does not?
They can use different access and synchronization routes even on the same device.
Go to the source
Documentation consulted for the routes and terminology on this page. Product behavior can change; verify your exact setup.
Kobo: syncing an eReader and Kobo Books appWritten by Binge Reader. Our comparisons explain documented workflows and practical tradeoffs; they are not independent product benchmarks.