I\'ve got a VS2017 project that compiles to a DLL which is then called by an EXE written by someone else. Both projects target .Net Framework 4.6.2. I rewrote one of my DLL
I experienced the same error "Could not load file or assembly System.ValueTuple.dll..." on my Windows Server 2016. However, the site worked fine on my dev machine.
My solution was simple, I grabbed this dll from my dev machine and dropped it in the site's "bin" folder on the server. It worked.