Thank you for contacting WPML Support. Thanks for providing the screenshot and details. For translating the copyright text in Flatsome theme, please try to follow the below doc:
1. Go to WPML >> String Translation page.
2. Scroll down and click on the Translate texts in admin screens » link at the bottom of the page.
3. Search for the required string.
4. Select the string. (If the string is already "Registered and locked" as in attached screenshot, please skip the step 4-6 and move to step #7)
5. Click on the Add to String Translation button.
6. Then click on the "« Return to String Translation" link.
7. Add the translation from WPML >> String Translation page.