Using backspace key to delete highlighted text in Word - not working

Hello All. In Word I used to be able to highlight text and then use the backspace key to delete the whole group of highlighted text.  The key still works in terms of deleting the letters to the left at the end of the sentence, but it just will not delete highlighted text (where I have highlighted using shift and left cursor key.

 

And now I am very confused   because the backspace DOES do this in this text box that I am typing now!!! so is it a Word thing rather than keyboard or is it the keyboard being temperamental - or is it a settings problem? Can anyone help? I have been advised to try this forum... thank you.