If you intend to receive screenshot attachments via email of users screens when Shield Alert Rules are triggered then you need to enable screenshots within the G Suite Admin Console.
To enable screenshots:
- Using your super admin-level credentials, log into the Google Admin console at admin.google.com.
- Click on Device Management.
3. Click on Chrome Management, under the Device Settings heading on the left side of the screen.
4. Click on User Settings.
5. Select an OU containing users who you want to receive screenshots from.
6. Scroll to the Content heading and Enable screenshot.