How to solve "An unhandled exception of type 'System.ComponentModel.Win32Exception' occurred in System.Windows.Forms.dll"?

Question

I am still a beginner to programming. I used to add a sliding menu to my program using c# bunifu framework. Once I clicked on a button on my sliding menu to open an another form with the help of creating an object I always receive this error,

An unhandled exception of type 'System.ComponentModel.Win32Exception' occurred in System.Windows.Forms.dll

Here is the code,

private void engineReg_btn_Click(object sender, EventArgs e)
        {
            DEOEngineReg DEOER3 = new DEOEngineReg();
            DEOER3.Show(); //Error refers here
        }

Thanks.