I'm not an IBM MQ .NET expert but some things don't look right.

Environment.SetEnvironmentVariable("NMQ_MQ_LIB", @"C:\Program Files\IBM\WebSphere MQ\bin\mqic.dll");

1. That path is for an older release of IBM MQ (aka WebSphere MQ). Why aren't you using the latest release IBM MQ v9.4?
2. That path is pointing to the 32-bit release of the MQ client library. So, your application is 32-bit and not 64-bit?

Environment.SetEnvironmentVariable("MQCHLLIB", @"C:\Program Files\IBM\WebSphere MQ\ssl");

You put the CCDT (TAB) file in the "ssl" directory? That's a strange place for it.

Environment.SetEnvironmentVariable("MQSSLKEYR", @"C:\Program Files\IBM\WebSphere MQ\ssl\cert");

Aren't you supposed to put the path plus cert name (without the ".kdb") in the environment variable?