Enter your Expo ID and password on the login page, then click ‘Click here to reset your identification method’ on the one-time password authentication page that appears after you click the login button. You can set your identification method 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