This yet again has nothing to do with my blog, but since I am running a website with elementor's plugin I wanted to help anyone else facing this foolery.
So your "edit with elementor button" disappeared, and doesn't show up when you try to add new posts or pages? This might not work for you but it worked for me.
Here's what you do...
1. Delete, and obliterate the cancer that is "Guttenberg Editor." Throw it away. "Guttenberg Editor" is Utter trash messing everything up. Leave it in 2018.
2. Go to add new, and type in editor.
3. Install, and activate the classic editor.
4. There, the button is alive!
Stay away from the cancer that is "guttenberg editor"
Hope that worked for you guys.