Can't place bookmark in text

[TYA]

Great day everybody.

 

I've tried a dozen times to place a bookmark in the versions to the left and the right, but although the bookmark icon appears when I begin to press the shortcut, the icon never sticks (as shown in middle version above), and these versions (left and right) never get bookmarked. I've checked the Library over and over, and nothing I've tried lets these get bookmarked. Why not?

 

See attached please.

Thank you.