Why is publishing and updating scenarios disabled in Publisher?
This is due to transition from single file addons to mods (unlimited size, multiple files) on Steam Workshop. Scenarios have been published using the old RemoteStorage publishing method. In the cases of an update or a new publishing, the old-method files would be switched to the new UGC method. And that's something we don't want just yet.
We have disabled the update and publish scenarios (on the creator's side) rather than breaking the experience for the workshop subscribers, until the new method is implemented in all applications to ensure smooth transition and backwards compatibility.
This temporary restriction is only relevant to Workshop items tagged as scenarios, because they can be loaded into game on the fly.
If you want to update you scenario or publish a new one, you can still do it from the Arma 3 Editor.
We apologize for the inconvenience.