Issue: Banner image changes in the Shopify Dawn theme didn’t appear on the live homepage after updating via the Theme Customizer. Refreshing and even updating the theme to 12.0 did not resolve it.
Fix: In the Customize editor, use the top selector to switch from “Default” to your country-specific page/homepage, then update the banner image, save, and refresh the site. This aligns edits with the correct market/page variant so they show on the storefront.
Outcome: The original poster confirmed this solved the problem and shared the steps publicly. Another participant confirmed the solution worked for them as well. The thread is effectively resolved.
how to fix this problem???
everything was just fine before..
but today i wanted to update my image banner in the theme customisation and all went good
but when i refresh my store website nothing changed!!! ..the old image banner still there!!!
i need someone to help me with this problem
i updated the theme to 12.0 but still the problem remain there
I NEED HELP!!!
i solved the problem
when you go to the customize page at the top of the page there is two option you’ll see the defult and home page make sure to change the defult to your country page and then change the banner image and save ..do refrish to your website and tada it’s working
so i don’t know why you both asked me to contact you in private
you guys supposed to give me the help in this page 
anyway this troublshoot helped me hope it helped u who ever read this thread
OMG, thank you! It finally worked after 100000 hours lol.