Powershell fails to load DLL because manifest is missing

These statements:

[Environment]::Is64BitProcess

[Reflection.Assembly]::LoadFile("C:\MvxAPI\MvxSockx64.dll")

Generate:

True

Exception calling "LoadFile" with "1" argument(s): The module was expected to contain an assembly manifest. (Exception from HRESULT: 0x80131018)
At C:\GitRepo\PowerShellScripts\ApiDllTest.ps1:11 char:1
+ [Reflection.Assembly]::LoadFile("C:\MvxAPI\MvxSockx64.dll")
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
    + FullyQualifiedErrorId : BadImageFormatException

From a PowerShell program I've written, I am trying to send transactions to the ERP system (Infor's M3) via a DLL for APIs. The DLL is provided by the manufacture. Since I am not a system admin but just a nerd supporting the ERP system, I'm clueless as to what I'm doing and have gotten this far with Google but can't get any further. Your suggestions will be greatly appreciated.