When you use Manual Site Collection Storage Management for the SharePoint Online sites, the sites don't automatically update to allow for the new 25 terabyte limit.
To resolve this problem, you must manually increase the storage limit quota for sites. For more information about how to do this, see Manage site collection storage limits.
This issue occurs because, when you use Manual Site Collection Storage Management, you must increase the storage limit quota for sites manually.
NOTE: This scenario applies only to the Site Collection quota.
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