It happened again although I’ve done it the same way your video “so you do it right” recommends. I don’t want to translate everything new after an update.
I updated your theme via WordPress and every translation/language in Loco Translate got lost. Now I have to translate it again. This happened already as you can see in the linked topic.
Have you made the full backup of the site? If yes, restore the site from the backup, move your translations to folder wp-content/languages/themes/ as per our video tutorial to prevent this https://www.youtube.com/watch?v=D3NsDdMzsls