Steps done:

1. Standard C# program was made (actually, it’s
   https://learn.microsoft.com/en-us/aspnet/core/tutorials/grpc/grpc-start?view=aspnetcore-8.0&tabs=visual-studio).
   That works.
2. A C++/CLR .NET class library was made (I need to keep
   some code ‘invisible’ from the users of the executable, not possible
   with C#, IP-reasons…).
3. I want to call a static method from the C++
   class.
4. I made sure both C#/C++ use the same .NET version
   (see answer here Managed C++ namespace not accesible in C#.Net during compilation)
5. The C++ is correctly (I assume) referenced by the C# module, else
   compilation would already fail.

When I start the C# program, I get the following error:

System.IO.FileNotFoundException HResult=0x80070002 Message=Could not load file or assembly 'grpc_server_processing, Version=1.0.8900.14343, Culture=neutral, PublicKeyToken=null'. The system cannot find the file specified. Source=<Cannot evaluate the exception source> StackTrace: <Cannot evaluate the exception stack trace>

The C++ DLL is where it should be, I also tried copying the DLL to the same folder as the C# executable, same error. Starting C# executable outside Visual Studio: same error. The version number of the DLL in the error message is the same as I see in Visual Studio in the object browser:

I have no idea what could be wrong, any help is very welcome.