Created an app, added the sid and secret, but still get { message: 'Customer not found.', code: 403 }

Usage below:
```
import { SlidesApi } from "asposeslidescloud"
const slidesApi = new SlidesApi(<sid>, <secret>)
const res = await slidesApi.mergeOnline(<files>)
fs.writeFile("MyPresentation.pdf", res.body)
```