"Preparing SageMaker Domain...may take a few minutes" for an hour?

An hour ago I initiated the creation of an Amazon SageMaker Domain for my class of students. Since then I have had a blue box at the top of the screen that reads,

"Preparing SageMaker Domain. Please do not close this browser tab. We are configuring the resources needed by the domain. This is a one-time configuration and may take a few minutes."

...and a spinning icon at the bottom of the screen that's still spinning.

I tried pointing a different browser window to that page while leaving the original running (I was scared to press Reload), and I see the same thing there.

What now? What recourse do I have? Thanks.