Using Office 365.

Recently, my Remove Background tool has been misbehaving. Generally, I click the image, select the tool, and the pink mask appears over my image, with a bounding box. Dragging the move points of the box expands or contracts the areas to keep (or discard). Often, just dragging the box is enough to identify the correct areas to keep and discard.

Just today, the bounding box is gone. Without it, I am reduced to using the Mark tools - much more tedious.

I have restarted PowerPoint to no avail.

Suggestions?