After I enroll in the Advantest Health Insurance Society, when will I be able to use the My Number Card as Health Insurance Certificate? I have already completed the procedures to register the My Number Card as the health insurance certificate (linkage with the health insurance certificate).

Once your employer (company) submits the notification of acquisition of insurance status or other documents to the Health Insurance Society, it will generally take five days or less until you can use your My Number Card as Health Insurance Certificate.
When you use your My Number Card as Health Insurance Certificate for the first time, you should access Mynaportal and confirm that your updated eligibility information is reflected in your health insurance certificate information.