This thread is resolved. Here is a description of the problem and solution.
Problem: When I go to https://www.huddersfieldtextiles.com?lang=ar to check it is working, it comes up in the Arabic language but it shows as a blank page and not the home page. The dropdown for the switcher isn't working either on our home page, however it works when I add the https://www.huddersfieldtextiles.com?lang=ar address. Solution: Everything works fine when changing the language to Arabic: https://www.huddersfieldtextiles.com/about/. All the other pages are not translated yet since all the pages from here https://www.huddersfieldtextiles.com/wp-admin/edit.php?post_type=page still have the plus sign for all the languages. Once you add the translation for your pages, the language switcher will definitely show the language, as it happens for the About page.
This is the technical support forum for WPML - the multilingual WordPress plugin.