Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Dear @Jingyou Chen
First, go to Services & subscriptions and check that your Personal subscription is active:
When you switch from Personal to Family, the remaining time on your Personal subscription is converted and added to the Family subscription. For this specific switch, 92% of the remaining time is converted.
Microsoft also has a step-by-step guide specifically for upgrading from Personal to Family:
If you purchased your current subscription through Apple, Google Play, or another third-party provider, you may need to manage the subscription through that provider instead.
Best regards,
Bence