When setting up G Suite sign-in for iOS on the Mobile guardian application please remember to trust the Mobile Guardian application in your G Suite admin console.
In you G Suite Admin console please navigate to Google Admin > Security > Assess and data controls > API Controls > MANAGE THIRD-PARTY APP ACCESS
Click on "Add App" > Select OAuth app name or client ID
In the search field please add the following link and click search: 429455869138-1bst228b6oinjjuvj5f02013jedhcovj.apps.googleusercontent.com
You will see the Mobile Guardian Application in the list, please select
Please check both checkboxes and click select.
On the App Access screen please select "Trusted" and click configure.
You should now see the Mobile Guardian iOS Application in the list of Third-party apps listed as trusted.