Screen readers read slide contents beginning with the title and then in the order elements were added to the slide. If you added images, objects or text boxes outside of the template layout, check the order.

To check and rearrange the order, select Home > Arrange > Selection Pane.

Arrange button in Windows.
Arrange button on Mac.

The Selection Pane appears on the right and shows a list of every object on the slide.

The reading order is from the bottom up. That means the last element in the list should be the bottom element.

You can reorder the elements by selecting and dragging them. In Windows, you may also use the arrow buttons.

Note: using the arrange options in the Arrange menu (e.g. Bring to Front) will move the object in front for the viewer AND move it in the reading order. If you use one of these, make sure to check the reading order in the Selection Pane.

Arrange panel in windows contains a list of the objects in the slide.