I had my site started and it was working correctly. Now it is only showing the text of my page copy. Backgound colors, masthead image, is not showing. Also the backlight admin page doesn’t load. I get the too many redirects error on that page. I made no changes since it was working correctly. Of course my web host says the host platform is all OK. I am using php 7.4. Any ideas about what could have happened?
What’s the url to your site?
Do you know if all modules are up to date?
Unknown about the modules, but I have my site back to normal. I made a back up of my site, restored to the backup. This made no change to the symptoms. The restore process put a .json and an .htaccess file at the same level as my public_html folder. After I deleted these two files my site was working as it should. 
If your whole site is running on Backlight and not just the galleries, then you need the .htaccess file in the root of the site (in the public_html folder) for things to work properly.
But we’d need to know where you site is to be of any help.
I have backlight’s htaccess file within the public_html folder. The one I deleted was up one level. It is working now. https://illuminimage.com