You have created a DLP policy for clipboard monitoring of a keyword (for illustration purposes, let us assume this keyword is 'example') monitoring and a pop up response rule.
You receive a pop up on the 1st attempt to copy the keyword; However, subsequent attempts do not generate a pop up irrespective of the time elapsed.
If you copy another sentence/characters with the keyword as a substring (e.g. 'This is example1'), the pop up appears just once, not to be reappear unless a different string is copied with the trigger keyword.
DLP 15.8 and above
Once a clipboard text triggers the pop-up, new pop up will not appear unless the text copied in the clipboard is different from the existing clipboard.
This is by Design. There is no advanced setting to override this behavior.