I received this error message after successfully creating a new entry on my iPhone and then repeatedly attempting to sync from iPhone to iMac. When that didn’t work, I deleted Codebook for iMac, re-installed a new copy from app store, and re-tried. No luck again - still same message. iPhone backup to Google Drive works fine. This leads me to believe problem is on the iMac.
What does the error message mean? Any ideas for how to fix this?