I’ve been saving and publishing project files to Project Online for a few years now. For some reason my publish button is no longer showing up in the backstage in MS Project. I am connected to project online. I can save and check in projects to project online. Files seem to be fine. Just no Publish button.
I had what might be a similar issue where when I would go to FILE it would default and show the Publish button and then the default view changed when hitting FILE. The publish button is in the INFO area. So my workflow is FILE, INFO, then PUBLISH. Hope this helps