This is probably me being stupid but what am I doing wrong here? I'm not sure if I need the code but I'm doing this in Visual Studio 2019.
Are you sure you specified both assembly versions correctly in the linker? This means both for release and for debug.
Considering that you are using VisualStudio2019, I strongly advise you to use vcpkg - this is a package management made by Microsoft that simplifies the installation of libraries and other features in 1 line =)
Using it, you do not even need to enter the linker, and the official vcpkg website will help you configure it correctly.