Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Hi, I'm John! I will help you with this.
Was the Gmail address your family member is using set up as a Microsoft account? It needs to be registered as a Microsoft account in order for the sharing to work.
If is already set as a Microsoft account please see the steps again here: https://support.microsoft.com/office/share-your-microsoft-365-family-subscription-b389b9ce-3ae3-4a82-9017-39d79972fcba
Let me know how it goes.
Click "Add comment" to let me know.
Regards,
John J.D.