Kobo Sync | Could not parse locale "*": expected only letters, got '*'

[peachdoughnut]

Describe the bug/problem

After spending countless hours searching in GitHub last night, I'm not able to properly sync my Kobo Libra 2 to my Calibre-web instance. I've already searched for all issues related to this problem in calibre-web repository, but none of the solutions fixed my problem. Things that I've tried:

• Check option "Proxy unknown requests to Kobo Store".
• Change ports to 443 or 80 (and also check in each the option "Proxy unknown requests to Kobo Store").
• Force a sync on the Kobo device (admin panel)..«
• Deleted app.db.
• Reinstalled calibre-web.
• Rebooted Kobo device.
• Corrected time in my Kobo Device.
• Manually converted ePub format to KEPUB in Calibre Desktop, before moving the book to calibre-web.

I was only able to reach the current problem (Could not pase local ....) due to the fact that I've changed the API url from http://[IP]:[PORT]/kobo/[Token] to http://[IP]:[PORT]/kobo/[Token]/v1/library/sync/v1/library/sync in the api_endpoint.

Settings in my Calibre-Web Instance:

I haven't setup a user account for Kobo. Instead, I've edited the user table in KoboReader.sqlite to show the following information:

This allowed me to enter my Kobo with no account created on the Kobo website.

Basic configuration menu

• Admin is allowed to make downloads/uploads.
• Enable Kobo Sync is checked
• Proxy unknown requests to Kobo Store - Unchecked
• Server External Port (for port forwarded API calls) - Same as my [IP]:8083 web-ui access

Admin Profile

• Kobo Sync token generated and correctly edited in Kobo eReader.conf
• Link being used: api_endpoint=http://[IP]:8083/kobo/[Token]/v1/library/sync
• Sync only books in selected shelves with Kobo checked

Shelves

• Sync this shelf with Kobo device checked

To Reproduce

Steps to reproduce the behavior:

1. Go to Sync in my Kobo Device
2. Click on it
3. Sync failed. Please try again

Logfile

[2025-04-13 12:00:56,326] INFO {cps.ub:764} 0 sync entries deleted
[2025-04-13 12:01:12,748] DEBUG {cps.cw_babel:27} Could not parse locale "": expected only letters, got ''
[2025-04-13 12:03:24,822] DEBUG {cps.updater:331} Stable version: 0.6.24
[2025-04-13 12:03:30,742] DEBUG {cps.helper:1012} UnRar version 7.11
[2025-04-13 12:03:30,745] DEBUG {cps.config_sql:388} _ConfigSQL updating storage
[2025-04-13 12:03:30,768] WARN {cps.config_sql:364} Log path not valid, falling back to default
[2025-04-13 12:03:38,921] DEBUG {cps.cw_babel:27} Could not parse locale "": expected only letters, got ''
[2025-04-13 12:03:56,453] DEBUG {cps.helper:1012} UnRar version 7.11
[2025-04-13 12:03:56,455] DEBUG {cps.config_sql:388} _ConfigSQL updating storage
[2025-04-13 12:03:56,478] WARN {cps.config_sql:364} Log path not valid, falling back to default
[2025-04-13 12:05:14,591] DEBUG {cps.updater:331} Stable version: 0.6.24
[2025-04-13 12:11:20,047] DEBUG {cps.updater:331} Stable version: 0.6.24
[2025-04-13 12:30:33,136] DEBUG {cps.cw_babel:27} Could not parse locale "": expected only letters, got ''

Expected behavior

Shelf books in calibre-web instance to sync with Kobo Libra 2

Environment (please complete the following information):

• OS: Unraid 7.0.1
• Python version: 3.12.3
• Calibre-Web version: 0.6.24 2024-11-16T07:21:28+01:00
• Docker container: linuxserver/calibre-web

Additional context
Not using any reverse proxy service, directly accessing trough my home network.

[OzzieIsaacs]

The message „ Could not parse locale "": expected only letters, got ''“ is correct, can not be avoided and has nothing to do with your problem.
You could try to update to the newest nightly version and check again.
Have you seen this: https://github.com/janeczku/calibre-web/wiki/Kobo-Integration#checking-kobo-sync-content

[peachdoughnut]

Thank you for the help @OzzieIsaacs. I have updated to https://github.com/linuxserver/docker-calibre-web/releases/tag/nightly-4e67a56e-ls267. The issue still persists.

I went to the url [server-ip and port]/kobo/[kobo_token]/v1/library/sync and I have the download link present. However, when I click on it on my browser, it adds the .epub extension to my .kepub ebook. It is the expected behavior?

Secondly, I never get this in the logs -> [2022-03-24 18:25:57,201] INFO {cps.kobo:140} Kobo library sync request received. Is it normal?