Typically, the 4.0 should have the 2.0 libraries as well, but it doesn't hurt to deploy the 2.0 Framework on your PC.
Download the version needed and install it alongside the Net Framework 4.X that is already installed on your PC. For example, I have 4 versions of Net Framework installed, just to avoid issues with compatibility since I am installing apps on a daily basis.
Reboot the PC and then try running Rayend again.