CityBook theme and its Add-Ons plugin are frequently updated with new texts added. So after update theme, plugin you have to use Sync button on Loco Translate plugin to get new texts
And to keep your translations safety, please make sure that the your files are saved in System folder: Root/wp-content/languages/plugins/
For existing translations, you can use Copy button to make a System saved version. And the system version is loaded first.
Can’t find translation texts?
Don’t forget change the plugin’s settings for large file