Firebase issue

Required - firebase expert who is able to fix a persistent issue.

In order to ensure firebase credentials are hidden in the console, they have been added to a .env file.
The code is bundled up using webpack.
When the project is built, console log prints the api key but returns an error - to do with import of firebase/firestore.app
As I am new to firebase am unable to find a correction.
I suspect this is 15 minutes work for the right person.
Thanks.