What to do when staging is disabled
Database merging is a unique feature of VersionPress.com, under constant development. As such, it might be occasionally disabled which affects your ability to create a staging environment or to push from it to live if you already have it. We also sometimes disable staging for specific sites, for example, for performance reasons.
If this blocks you, there are a couple of workarounds are available. The key point is that the staging environment on VersionPress.com is a full WordPress site in its own right, with all the features like SFTP, SSH or Adminer enabled. Likewise, staging can be temporarily emulated via a separate free site.
So while you might lose the convenience of pushing / pulling between environments for a while, all other, pre-VersionPress techniques are available. Let's focus on a scenario when you want to move your staging contents to the live site.
Repeating the task in a live site
Sometimes, it might just be the simplest to repeat an action manually. For example, if you verified that a plugin or theme update is OK, you can update it directly on the live site.
Using WordPress exporter / importer
WordPress has a built-in export & import tool which you can use to move data between environments.
If you love command-line, you can migrate using WP-CLI commands.
Using WordPress plugins
There are myriads of WordPress plugins that help with export & import, this articles provides a nice overview.