SharePoint: site Quota threshold exceeded, but no notifications received

Hi, I would first confirm that the tenant is using Manual site storage limits and verify the actual StorageQuota, StorageQuotaWarningLevel and current storage usage for the affected site. Also confirm that the expected recipients are current site administrators with functioning, licensed mailboxes rather than only a group or an old owner account. After confirming the values, change the warning level slightly, save it, and set it back to force the configuration to be written again. Built-in quota emails are useful, but I would not rely on them as the only operational alert. For important sites, a scheduled PowerShell, Graph or Power Automate report that checks storage usage and posts to an administrator mailbox or Teams channel is much more visible. If the built-in notification still fails, open a Microsoft 365 support case with the site URL, quota values, owners and the date the threshold was crossed.