MMM-Google photo error when executing node generate_token.js

[ruud]

I’ve installed the MMM-Google photo module on a windows pc with git bash
I’ve created a client_secret_xxx.apps.googleusercontent.com.json file and renamed it to credentials.json and placed it into the MMM-Google photo module directory.
The problem occurs when I execute node generate_token.js. See the error below. What is wrong and how do I fix it?

$ node generate_token.js
[GPHOTOS:CORE] Error: Missing Credentials.
C:\Users\administrator\MagicMirror-master\modules\MMM-GooglePhotos\GPhotos.js:13
3
throw e
^

Error: Missing Credentials.
at new Auth (C:\Users\administrator\MagicMirror-master\modules\MMM-GooglePho
tos\GPhotos.js:31:11)
at GPhotos.onAuthReady (C:\Users\administrator\MagicMirror-master\modules\MM
M-GooglePhotos\GPhotos.js:130:14)
at GPhotos.generateToken (C:\Users\administrator\MagicMirror-master\modules
MMM-GooglePhotos\GPhotos.js:141:10)
at Object. (C:\Users\administrator\MagicMirror-master\modules\MMM
-GooglePhotos\generate_token.js:10:9)
at Module._compile (internal/modules/cjs/loader.js:1138:30)
at Object.Module._extensions…js (internal/modules/cjs/loader.js:1158:10)
at Module.load (internal/modules/cjs/loader.js:986:32)
at Function.Module._load (internal/modules/cjs/loader.js:879:14)
at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js
:71:12)
at internal/main/run_main_module.js:17:47