Hi Medes71,
>>I have an office 365 tenant and I have created a App Catalog Site Collection.<<
As far as I know, there are three ways to publish a taskpane or content app( Office Store, app catalog, a shared network folder). Did you mean that you publish the apps of a SharePoint online?
If I understood correctly, did you upload the menifest to the Office catalog on SharePoint?
You can get more detail about pulish apps for Office to app catalog:
How to: Publish task pane and content apps to an app catalog on SharePoint
How to: Set up an app catalog on SharePoint Online
Regards & Fei
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