It feels clear to me, in my searching for an answer, that there is a file somewhere in the chain of launching the editor that has the default block editor being replaced with the classic editor. Classic plugin is not installed. What is the best way to find which offending file is making this change? I am guessing there aren’t many files that have an opportunity to do this, once "add new" or "edit" is selected, but have not yet been able to find a list of files that have the power to do this, if you will. It is tied to the custom theme being used with Divi. When t-shooting, using the 2021 theme, the block editor works. Also checked the functions.php file in the offending themes folder and did not see anything obvious. Any enlightenment would be greatly appreciated.
Note: I am a novice with this and certainly have plenty of ignorance waiting to be replaced with knowledge.