I had a look at the site this morning and here are a few more notes.
I’d definitely suggest turning on error reporting to get a more useful error message. See: https://omeka.org/classic/docs/Troubleshooting/Retrieving_Error_Messages/
Looking at the source, it appears the page loading fails where the header is looking to output the title for use on Twitter cards (see screenshot below). I’m not sure what to make of that
Based on the little that is actually loaded before the error, it seems you’re loading in a custom Google Font and have modified the CSS file in multiple places with the font commented out, i.e.
/*font-family: 'Cormorant Garamond', serif;*/. While this doesn’t in itself explain anything, it suggests you may have some customizations elsewhere that aren’t working as intended. This is just a guess since I can’t see your actual theme code. Do you know if you’re using Curatescape theme as delivered or if it includes modifications?
You should also have a look at the
Admin > Plugins area to ensure that the final steps for plugin upgrades have been completed (i.e. are any of the plugins highlighted in green with an “upgrade” button?).
Does saving your theme settings have any impact?
Again, enabling error messages is a good first step, and updating the theme to the current version is also a good idea, assuming you don’t mind losing any hard-coded customizations.