hell Nnamdi,
I was facing the same problem. Having done everything I thought I had to do, the new application did not appear in staging.
This is what you need to do (credits go to Odoo Support).
When your merge a dev branch to a staging (or production) branch, the purchased app is not automatically installed on that version of your database. You have to add it manually.
Steps to follow:
- drag and drop the app to staging
- connect on the staging branch
- activate the developer mode
- go to apps and click Update Apps List
- install your app
I hope this will help some of the users facing the same problem.