A Microsoft file hosting and synchronization service.
Sorry to hear that you are having trouble with this situation. Could you please share a little more information about what happens when you try to add members to your Microsoft 365 Family subscription? Do you receive an error message? If so, please share a screenshot of the error, making sure that no personal information is visible.
Also, please sign in to https://account.microsoft.com/services using the same Microsoft account/email address that was used to purchase the subscription and let me know whether the 100 GB subscription appears there as active. If possible, please share a screenshot of that page as well, again hiding any personal or billing information.
Regarding the OneDrive storage, please let me know whether you are checking the available storage inside the OneDrive app or directly at OneDrive.com. If you are checking in the app, please also check OneDrive.com, as the updated storage allowance may sometimes appear there sooner.