Another NewB problem

I just installed 2.035. Running Delphi 12.3

When I try to load a user assembly, I get the following error:

Unable to load assembly:
[ReflectionTypeLoadException]
Could not load type
'System.Runtime.InteropServices.ICustomMarshaler' from assembly
'System.Runtime.InteropServices, Verson 4.0.0.0, Culture=neutral,
PublicKeyToken=bb03f7f11d503a'.


I have loaded GAC assemblies mscorlib and System.Runtime.InteropServices.


System Info

RAD Studio 12 Version 29.0.53571.9782
Windows 10 (Version 22H2, OS Build 19045.5247, 64 bit Edition)

.NET 9.0.101
16GB Ram