You can autodiscover Microsoft OneDrive for Business user accounts from a user-defined user group, using regular expressions or wildcards, or Azure affinity groups. However, there will be a few user accounts that will neither match the regular expressions nor the Azure affinity groups that you entered. By default, these undiscovered user accounts are not added to any user groups.
You can add the undiscovered user accounts to the default user group.
From the navigation pane, go to Protect > Applications > Office 365.
The Office 365 apps page appears.
Click the OneDrive for Business app.
The app page appears.
In the Infrastructure settings section, move the Add users that do not match any auto-discover rules to default subclient toggle key to the right.