In order for an individual user to access files located on a Google Drive, the school must provide a Google Project to manage the process and provide secure access. There are four steps that must be completed in order to create a Google Project and activate Google Drive access for your users.
Go to Core > Settings > Integration settings > Google Drive for information about setting up a Google project, Enabling APIs, etc.
When setting this up with Google, the myschoolapp.com address needs to be used and not the public facing URL.
Not setting this up properly will cause users to get an error (usually a 400 error) and will be unable to access Google Drive.
Correcting this setting in Google should make accessing Google Drive work correctly.