Play a lot of (blitz) games. You likely just need more practice in game settings. Understanding Chess Tactics by Weteschnik might be useful. That book helps you learn how to see the indicators that a tactical shot might be present.

Oh, also - How many times did you do the problems in CT-ART? I've found repetition is extremely important in tactical training. i.e. Do the 10, 20 and 30 "difficulty" problems 5 or 6 times each and see if that helps.

I need some advice please.

I’ve gone thru CT-ART with over an expert rating (2059). Place a book/board in front of me and tell me mate in 2, mate in 4, or white wins material, etc and I can usually get it. However, in a tournament, with the clock ticking, I tend to miss these tactical opportunities or I see them too late. 
How can I improve this area of my game so I can recognize these tactical shots without neon signs flashing overhead???