I will also add that between the time it was working correctly and when it disappeared, I did not install or enable any extensions that could interfere with the display of blocks in the insertion panel.
When I was building the site, everything was working fine and I was using these blocks. However, I don’t know when or why most of the Greenshift elements suddenly disappeared from the inserting tab in the editor. The ones I used work correctly, but I can’t find and add them now. Below are screenshots from the Gutenberg editor with Greenshift.