File was not accepted by any of Envelope Engines.

Hello,

I'm using Sentinel LDK Envelope 7.4 tool to protect our dll files.  But I got a error: "File was not accepted by any of Envelope Engines".  It's a C# dll which is included some C++ assembly.  I'm sure that this program could be launch in the same PC installed Sentinel tool.  How could we solve it?

Thank you

PNWang