As per Taiwan authority’s new control requirements on inbound roaming,

all data card users must complete real-name registration before continuing to use data service in Taiwan, starting from 10 November 2023. Users can go to telco website and complete the real-name registration by uploading identification documents.

You may check the registration guide via this link:

https://www.icard.com.sg/pages/real-name-registration-faq-for-tw