I ran into the following error:
TypeError: Cannot call method 'config' of undefinedThere was an import statement that I had to add to a main.js file
It turns out I had added the import line into the wrong 'main.js' file.
There are 2 main.js files: One in the client folder and the other in the server folder.
Once I moved the import statement to the client version, the app started working again