This project is set up to use Cloud Firestore in Datastore mode. This mode can only be accessed from Google Cloud Platform

This message indicates that your database was created in Datastore mode, when you created your project. You should be able to change it by accessing the Datastore Console using this link here and clicking in the available button to switch the mode - check here. However, as clarified in this other post from the Community here, you can only do it once and if you have not performed any changes in your database.

In case you don't fit in these above scenarios, you will need to create a new project and configure Firestore from the beginning.

Let me know if the information helped you!