I am trying to pay with a corporate card, but it keeps saying ‘주민OR사업자등록번호 오류’.

It only applies to Korean credit card.

When entering card information, even if it is a corporate card, if a person's name is on the card, you must select 'Personal Card' and enter the date of birth. If the company name is on it, you must select 'Corporate Card' and enter the business registration number.