I have several global blocks. In the past you could click on one to see the preview in the right panel. Currently when I click it previews the home page.
I click the edit button of the global block and it does open cornerstone and I see the block to edit it.
I read previous post that it could be a plug-in conflict. I narrowed it down to Yoast Premium plug-in. All the themes, plugins, WP Core are the latest versions. All Caches cleared.
Have you experienced this on other setups?