When you are trying to search for a particular string, and that string is not visible in the Loco Translate plugin. So you need to hit on "Sync" Button. So that your PO and MO File will read the strings of POT File and sync all the strings.
Translations Completed Still Not Reflecting in Frontend
Please check your site language and then check in Loco Translate, if you are translating in the correct language or not