I don’t know how Divi works, so I can only guess at the problem from the error messages.
The maps API can only be loaded once. If the API is loaded by a theme or another plugin, it can cause a conflict with MapPress. This is described in detail in the FAQ.
The ‘missingkeymaperror’ indicates Divi (or something else) was trying to load the API without specifying an API key.
The solution is to disable maps API loading in Divi. There’s often a checkbox for this purpose, or you could contact the Divi authors to ask how to do it.