So after more troubleshooting (re-installing the theme, deactivating plugins, re-instating htaccess) which didn’t change anything, it turns out that an existing subdirectory was interfering with this subdirectory somehow. I suppose at one point I had pointed my site url to the old subdir and never cleaned up properly in the backend when I changed – the old subdir shares a similar name to this one. Thought I would mention this point as my site url has successfully pointed to other subdirs in the past with no issues. This issue was resolved after I deleted the interfering subdirectory and database.
Hope this helps someone facing similar issues in the future!
