@bodenburgc
I downloaded the client_secret file and copied it to my MMM-GooglePhotos directory.
Step 9 I ran the command as you did:
cd ~/MagicMirror/modules/MMM-GooglePhotos
node auth_and_test.js
It took me back to google account and it gave me the consent code to paste into the console.
It then listed all my albums I have on Google Photos.
MW