When a new theme version is released / updated, the translation .po must be updated as well to find the new terms – http://www.marketpressthemes.com/blog/how-to-merge-two-po-files-using-poedit/
Step #1
Open up your existing language PO file with Poedit software.
Step #2
Go to Catalog
and selectUpdate from POT file
Step #3
First, change the file type option to All Files
, then select the new wpestate.po PO file from latest theme update folder
Step #4 (OPTIONAL)
Next, you’ll see a mini box which includes all the new strings as well as obsolete string from the new PO file. Proceed by clicking the ok
button.
Step #5
Once the import is completed, all the new string from the new PO file will be added and your existing (translated) string will remain intact as well.
Step #6
Finally, proceed to translate all the new string into your preferred language. Save. Move the updated .po and .mo language file back to wpestate/languages or to child theme languages folder.