Your function is in the Player Controller:
The BP_Finish Line does not collide with the player controller - they have no collision:
I am assuming these are the cars that finish the race, right? So you’re asking the car to stop the timer it does not have. If it’s the controller that is running the function, ask it to stop it:
Also, none of this manual counting is needed:
If you used a timer as originally suggested, you’d have everything ready:
The timer counts the time and you can format the display it as you want. Consider watching a quick YT tutorial to see how it works.
Up to you, ofc. Good luck!