Thanks very much for using Codebook and posting the discussion forum.
To be able to sync with Codebook 4, all your devices must be updated to Codebook 4 and setup to use the same Sync Key.
You’ll need to update your iOS device(s) to Codebook 4 by visiting the App Store, searching for Codebook Password Manager and tapping the “Update” button.
After updating your iOS device(s) to Codebook 4, you’ll be presented with the Sync Key setup screens after logging in. You’ll want to choose “Yes” (I already have a Sync Key) since you already generated one on macOS, then import your existing Sync Key by following the steps here:
Let me know if this allows you to update your iOS devices to Codebook 4, and if you’re able to get up and running with sync.
I’ll be happy to assist if you have any questions or run into any issues along the way. Thanks!