search-form "go" button not showing text

Both of those elements have been marked for translation, so you should be able to change them via the translation files.

Or are you looking to change the text entirely, rather than translate?

Sorry, I made a mistake while writing.

The translations are fine.
If you look at the link I posted, you will see that the problem is that we can’t see the text in the button or over the input box. Like if the background was white and the text too.

I understand now. I actually don’t think this is related to the update. If you check out the live demo site, you’ll see the search widget still has the dark button background and no placeholder text.

There is likely a plugin or some other CSS that is affecting the display of the search form. You can try deactivating your plugins or temporarily removing any customizations to find the source of the change.

As an alternative, the following CSS could also be used to force the button back to the dark background:

.search-submit {
  background: #333 !important;
}

And this CSS will darken the placeholder text:

::-webkit-input-placeholder {
  color: #333;
}
:-moz-placeholder /* Firefox 18- */ {
  color: #333;
}
::-moz-placeholder /* Firefox 19+ */ {
  color: #333;
}
:-ms-input-placeholder {
  color: #333;
}

I figured out how to fix the button color, it was a mistake I made in the CSS. But I still can’t find how to display the “search” text that is supposed to be over the input box. Here’s how it looks like: https://i.imgur.com/qimD0XP.png

How can i have the text back ?

That is a translation of the default placeholder text. To modify that you could find and change the entry for it in the .po file and recompile the corresponding .mo file. Or, you could edit the searchform.php file (with a child theme), and manually edit the placeholder text you want displayed there.

The placeholder is fine.
Th problem is that I don’t have the “Search” text that is supposed to be over the input box.

Sorry I get it now. When editing the widget, you should be able to add “Search” in the title input, and it will then display above the search box. Please try that and let me know if it shows or not.

There already where a title, but when I deleted it and set it back up, it fixed the issue. Strange.. Thanks for your help !

Sure thing, glad it works now!