Microsoft Word Track Changes not Working

Hello Expert,
Admittedly this is my first time using Track Changes but it seems like it should be fairly intuitive.
Microsoft 365 Subscription Product is the version.
I go to Review > Tracking  > Track Changes and click on Track Changes in the drop down.
For Markup, Simple Markup is chosen. In Show Markup, Comments, Formatting, Balloons and Specific People are unchecked.
Insertions and Deletions is checked.

So to test a sentence was deleted. That is I selected a sentence with the mouse and hit the delete button.
Expected result: The selected text would be struck through.
Actual result: The selected text was deleted.

What am I doing wrong?

Thanks.

Allen in Dallas