This looks like you are trying to call this native .dll from a managed .NET program in Visual COBOL whereas you were calling it from a native program in Net Express, correct?
Are you compiling the OO program that you show above as managed code or is that compiled as native code? I am a bit confused because the syntax of the program you are showing uses the old native OO syntax and not the new managed syntax.
If you are calling a native .dll from a managed code program then they must be using the same bitism. That means that if SAT.dll is a 32-bit .dll then your managed project should also have a target of x86 and not x64 or anyCPU. If SAT.dll is a 64-bit .dll then your managed project should be targeting x64.
Can you check your project properties on the COBOL tab and tell me what the target CPU is set to?