Changed Site URL, Internal Server Error

Hi, I’ve built a site in a subdirectory but wanted it to become accessible from my root URL. I committed the classic noob mistake of merely changing the Site URL to my domain in the General Settings and now I can’t access anything.

However, I already HAVE tried most of the steps in Changing the Site URL. I edited functions.php via FTP with those 2 lines but it didn’t work. I then accessed the database directly through my hosting manager and changed siteurl and home back to the correct value (of my subdomain). Generally everything I have been able to find online just refers me to that article, but it’s not working and now I’m lost.

To make matters even more strange, I have a normal simple HTML/CSS site created in my root folder. That website is still accessible as normal. However, I have a total of 3 wordpress subdirectories on my domain and ALL 3 now result in internal server errors, even though I only changed the Site URL for one of them. Any ideas where to even start looking? I host with Godaddy (unfortunately) if that is any help.