If you can't, ask your IT person to unblock access to:
https://boom-cards.s3-us-west-2.amazonaws.com/

If your students' devices are not loading images, open this page in a browser on their device to confirm you can see the image.
https://wow.BoomLearning.com/help/

If you can't, check your volume and mute settings.

See if your school has granted permission to import Microsoft classroom rosters.
More info here