Hi @kimjunwoo,
Welcome to the forum.
Thanks for sharing the steps you’ve already tried.
Per the Models documentation, Gemini 4 Argon is available with paid Google AI Pro plans, Google AI Ultra plans, or on trial with eligible premium devices, while Claude Sonnet 5.5 (thinking) and Claude Opus 5.5 (thinking) are available on Google AI Pro for non-trial subscriptions only (and Claude Sonnet 4.6 is being retired on November 2, 2026).
Because model access for family members depends on the family plan manager’s subscription, please check whether your family manager’s Google AI Pro plan is currently on a trial or third-party partner offer. Per the Upgrade FAQ, trial and partner plans include the 5-hour Pro quota refresh on Gemini 3.8 Flash (Plans), while unlocking Gemini 4 Argon and Claude 5.5 requires switching to a paid plan via Google One Support (or managing partner plans via the third-party subscription guide).
If your family manager is already on a paid (non-trial) Google AI Pro plan and your expired trial is still affecting your account, please contact Google One Support to refresh your subscription benefits, or reply here with a screenshot of your Google One membership page.