у меня через WPML два языка ру и инглишь , WPML при свитче языков не меняет кнопку в шапке т.к я попросту не нашел ни в одной строке её
Often times the texts you add in the theme options are stored in Admin Texts. Please go to WPML > String Translation and scroll down to the bottom of the page and click on the link "Translate texts in admin screens »". Then, scroll through that page look for a section titled something like theme_mods_yourthemename. Expand the section and tick the checkbox next to the strings you want to translate and click Apply to add it to the String Translation table. Now you can go back to WPML > String Translation and you should see the string added there.
а так вы пробовали?