404 Errors?

Hey guys,

I woke up this morning to find that my homepage is missing pretty much all of the content except the sidebar and my posts, and, perhaps most importantly, all of my pages (including new ones that I create) are generating 404 errors.

Examples:
https://www.uchicagostudentagencies.com/about-us/
https://www.uchicagostudentagencies.com/marketplace-day/

Here’s my .htaccess file — I don’t think anything is wrong with it:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ – [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

# END WordPress

Permission settings are 0644.

My permalink structure is Custom Structure: /%category%/%postname%/

It worked perfectly fine until today…

If I switch the permalink structure to Default, MOST of the pages stop returning the 404 error, though the homepage and the Order page are still missing content.

This happened completely randomly over night, and I am about to pull my hair out.

Any ideas?