I can't take screenshots through steam

I can play BeamNG through steam, I can't take screenshots through steam, because BeamNG is not hooked up to my account in-game.
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The story: My antivirus Would not Load up BeamNG (The icon showed up that it was open but i could not access it) And I knew it was antivirus because It loaded up fine in the administrator account but not on my regular account. I fixed it, but everytime i load up beamng on my account, it has a screen something along the lines of:
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Do you want to allow the following program from an
Unknown publisher to make changes to this computer?
Owner Password:
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Then it asks me for the administrator password. When i enter the password BeamNG loads up fine, but Now in-game, You guessed it, I CAN'T TAKE SCREENSHOTS THROUGH STEAM!!

Please! I need help, because i love taking screenshots for the steam community!