Paid apps are not listed under the installed apps of a Confluence Cloud instance

Summary

After finishing payment for apps, they are not displayed under the Manage apps part of Confluence's administration.

Diagnosis

Have Atlassian or a partner activating the app on the user's behalf in order to generate a quote.

Cause

Apps that are activated by Atlassian in order to generate a quote so they can become paid will not be automatically installed unless the admin itself did it.

Solution

Manually install the app after having the payment done or, as a site admin, generate the quote so the app should be automatically installed.