HOOPS Visualize sandbox works with HOOPS Exchange integration as this page.
https://techsoft3d.atlassian.net/servicedesk/customer/portal/11/article/768049505
When you want to use HOOPS Exchange API directly in sandbox, you will need to load and initialize HOOPS Exchange library as followings.
https://docs.techsoft3d.com/exchange/latest/guide/start/initialize-hoops-exchange.html?
For more information check out our forum post.