Flag images broken

I added a shortcode to the top bar of the website to display the language switcher.

I used the code here to create the shortcode

https://www.grupojmll.es/genera-un-shortcode-para-mostra-banderas-de-idioma-en-polylang/

However, the flags are not displaying (a missing image icon appears instead)

Can anyone help me figure out why?

thank you!

The page I need help with: [log in to see the link]