Ken de cooman, did you have contact with official support?

I am having the same issue as Kenny Maurer. The upgrade button in database manager is not available in my Odoo online 16.3e database, even though Odoo online should be able to upgrade according to the official Odoo upgrade page. I have no third party apps installed, and have used some Odoo studio with light html modifs.

This is an urgent issue since we need to invoice as Peppol Access Point only available from Odoo 16.4e onwards.

Thanks for your inputs.

Go to your database manager and click on gear icon of your database. There you will see the upgrade option if it's available