The Add-in for Outlook automatically updates when a new version with minor changes is available. A manual update is required only when major changes are available, for which Cloud App Security will make announcements.
The version number of the Add-in for Outlook is in the format major.minor.revision, such as 1.0.0. The major number reflects major changes, while the minor and revision numbers reflect minor changes. Manual update is necessary when the major number changes.
In the Microsoft 365 admin center, the version number of the Add-in for Outlook changes only after a manual update, so it can be different from the add-in version number in Outlook.
According to Microsoft, it can take up to 72 hours for the update of an add-in to apply at your users' side.