When perform reverse engineering of .NET binaries you may experience a problem that the Visual Paradigm complain the file you specified cannot be loaded.
This problem could be caused by the security setting in your Windows that blocking the access of your .NET binaries. To solve this you can right click on your .NET binaries and select Properties form popup menu.
After that check the Unlock checkbox in the Security section and press OK to save the change.
Once this is done Visual Paradigm will able to reverse your .NET binaries.