Hello,

You need to find Login / Register string, not simply Login if you want to change that text in the header. We have just tested on our website and it works correctly
https://gyazo.com/ca1eca812fd0ed3f2df9f6f8b52d2572
https://gyazo.com/943d370b60d8ed9dd9a7eb0eefcfac8d

Try to get our theme’s origin PO file from the folder woodmart/languages and replace it in the same location on your website. Then remove all your other translations and create a new one according to our tutorial.

If it will not work for you, then we will not have any other ways to help you except get your admin access and check ourselves.

Kind Regards