Hello,
Admin demo store's default credentials are not working.
I cannot access and got an error
"Login was unsuccessful. Please correct the errors and try again.
No customer account found"
Below is what I use as per your GitHub
Backend
https://demo.grandnode.com/admin
Demo is restoring once per day to the original state.
Access to the admin panel:
Admin email: admin@yourstore.com
Admin password: 123456