Enter your Expo ID and password on the login page, then click on ‘Click here to reset your identification method’ on the One-time Password Authentication page that appears after you press the login button. You can set the one-time password authentication by logging in again from the login page.
If you are unable to reset it yourself, please contact us via ‘Enquiries about admission tickets and Expo ID registration’.

https://faq.expo2025.or.jp/hc/en-gb/p/contact