As long as you can see Precision's on-screen display in a game, you
should be able to capture a sceenshot.
What you might need to do is after assigning a folder and hotkey/s to capture, click OK, then close the settings..Then open the settings again to be sure the folder and hotkeys remain and are correct..Then start your game and try it..Precision and OSD settings have a problem saving some settings unless manually closed and opened again.
You might be suffering from some amount of Precision-induced keyboard lag in some games which is not uncommon and you need to hold down your hotkey/s a little longer..When I use hotkey combos (Alt + F1, F2, whatever.) I sometimes have to hold down the first hotkey for a second or two before hitting the second one..When using a single hotkey I sometimes have to hold it down for a second or two also or even hit it twice..I'm using Alt + C now.
If Precision which is kinda borked doesn't work well for you capturing screenshots you can try
GeForce Experience or
Fraps or
MSI Afterburner instead of Precision..I'm sure it's nothing you're doing wrong and it's Precision at fault..As with MSI Afterburner, some hotkeys/combos may be reserved and cannot be used.