If you're sharing Google One with your family and seeing the wrong amount of space, have the person in charge of your family plan check that the "Share Google One with family" button is turned on in Google One Settings > Manage family settings.
Make sure that everyone is in the same country, because sharing only works between people who are in the same country.
Next, remind family members that they should always use their own 15 GB first, then the shared pool. There is no set amount of room for each member; it is used "as needed."
If members still only see 15GB after accepting and turning on sharing, try turning sharing off and on again and then refreshing the Google One app or web. This usually fixes sync problems.
If the issues still happen after 24 to 48 hours, the plan manager should get help for their individual account by calling Google One support through the app or at one.google.com/support.
If the issue persists, share your experience and consider filing a complaint on Xolvie to seek a resolution.
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