Thanks for using Codebook and reaching out.
It sounds as if you may be using Codebook 3 on your Windows machine and Codebook 4 on your Android device.
Codebook 3 won’t be able to sync with Codebook 4.
Please update Codebook for Windows to Codebook 4: Updating to the Latest Version
Once Codebook for Windows is updated to the latest version, you can follow these steps to import your Sync Key from Android into Windows: https://www.zetetic.net/codebook/documentation/sync-setup-help/?platform=windows (under “If you have already created a Sync Key in another copy of Codebook”).
After the Sync Key is imported into Windows, attempt to sync again.
Let me know the results. Thanks!