The script don't inherit a native class that can manage a script.

Hi, I am using the latest Unity 2020 (2020.2.0.a13) and every time I try to attach a script it won't let me, complaining that "The script don't inherit a native class that can manage a script." I encountered this problem first time couple days ago, I don't remember if turning my pc on/off or closing Unity solved it. Now I am stuck with this issue, I tried what I mentioned above without success. Any suggestion?g) (I have created an empty script that basically just inherits from MonoBehaviour and tried to attach it to an empty gameObject, won't let me so frustrating)