Can't view pages – 404 error on many pages

Hi, whenever I access some of my pages (all except Home and Shop pages), I am linked to 404 page. It used to work fine but from some point, I keep getting 404 pages.

I tried setting the theme to default, deactivating all the plugins but it still didn’t work.
I tried adding a rewrite rule on htaccess file but that didn’t help either.

Could anyone give me a hand? Thanks so much.

https://inditravel.co.kr/wordpress/pages/about-us-v1/ https://inditravel.co.kr/wordpress/pages/faqs/
https://inditravel.co.kr/wordpress/cart/