for CS:GO, you should use game capture. window capture only of game capture isn't working. monitor capture isn't recommended for 90% of use-cases.
so try this:
1. remove any monitor captures (as they have issues with switchable graphics), window captures that you used to CG:GO previously, and go ahead and remove any game captures for CG:GO. We will add back a CS:GO game capture in step 4.
2. Follow these instructions:
https://obsproject.com/forum/threads/laptop-black-screen-when-capturing-read-here-first.5965/
3. create a new global source for game capture, start cs:go in windowed mode, alt-tab back to OBS and click refresh on the new game capture and select CS:GO (no need for anicheat hook or anything else like that) select stretch to fit.
4. right click on the sources for the scene you want. click global sources and select the game capture you created in step 3.
also, as Greendweller said, you have another program trying to capture CG:GO, whether that be a 3rd party overlay or another stream/recording program
this could be nVidia experience, overwolf, Razer Synapse, FRAPS, D3DGear, MSI Afterburner, Action!, TeamSpeak/Mumble Overlays or any other kind of FPS monitor or overlay program
nVidia experience, overwolf, Action! will need to be uninstalled, but the rest the in-game overlays can just be disabled.