Google Workspace Marketplace Settings

In the Settings for Google Workspace Marketplace apps, To allow users to install comeen you can select "Allow users to install any app from Google Workspace Marketplace":

Or if you choose "Allow users to install only allowed applications from Google Workspace Marketplace":

You need to add app on your allowlist.

For this, on your google admin, go to Apps > Google Workspace Marketplace apps > Apps list:

On this page click on "Google Workspace Marketplace allowlist":

Click on "Add app to allowlist" :

Search Comeen and click on "Add to allowlist":

The application Comeen has been added to your list of authorized applications.