so setting and resetting the gameover variable, works for the first part. if user still has bullets → game is not over as soon as the game is over and reaches EndLevel → set the bool to true → this will prevent the mouse click from firing again.
However, once EndLevel widget is loaded… whether the player finished or not, when I load the next level or restart the level, the do once gate seems to be closed and the player can no longer shoot. I tried setting the variable to false again, but it did not work.
To complicate matters even more, in PC on EventBeginPlay I have a DisableInput, which gets re-enabled when the HUD loads. (This part was working fine before) Not sure if this is what’s causing the input lock or the DoOnce not resetting the gate.
See images below…
When the game starts, in PC I disable input:
Mouse click for shooting:
In the HUD UI, I re-enable input. (this worked fine before I added the DoOnce node)
Now on subsequent levels, or if I redirect the user to the MainMenu and start playing the 1st level again, the input is locked 
(during the same game session)