Before your ticket is assigned to one of our colleagues, please allow me to walk you through some initial debugging steps. This will help speed up the support process.
Could you tell me how you're adding the text for the submit button? If you're using something like [submit "Send Mail"], it should be possible to translate it. Could you share screenshots of how you're adding the text?
Also, would you be open to making a small change to the contact form, sending it for translation, and seeing if that helps?
As you can see from the screens, even playing with the texts, the moment I open the translation editor the only text that does not come out for translation is the button text.
I think that the submit button's text created with CF7 comes from a shortcode attribute.
The shortcode attribute values are hidden in the advanced translation editor, so please edit the form translation and use the Search feature in the upper-left-hand corner to find the original attribute text and translate it.