First you have to try to diagnose it, might be just a file error.
open a folder and on the top bar search: %appdata%
that should open your AppData >> Roaming
in that Roaming Folder Cut the folder called "obs-studio" or "OBS" if you have OBS classic.
paste it anywhere else for safe keeping. (that folder will have all your saved scenes and preferences made to your OBS.)
Now you can either uninstall and then reinstall OBS, or run OBS to see if it runs okay. if it runs fine then it was something in your old OBS folder.
If this guide didn't fix it then leave your OBS folder in Roaming. Good luck!