Solved
As Coises pointed out above, when I commented the post build task for exporting the dll file I was effectively bypassing an important step. The task did more than just copy the dll to the npp/plugin folder. I added a comment to the task (see below) saying the following block of code could be uncommented to do that extra copy to npp/plugins folder.
<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003"> <UsingTask TaskName="NppPlugin.DllExport.MSBuild.DllExportTask" AssemblyFile="NppPlugin.DllExport.MSBuild.dll"/> <Target Name="AfterBuild" DependsOnTargets="GetFrameworkPaths" > <PropertyGroup> <!-- LibToolPath is optional - it's needed to debug C++, but you can still debug the C# code without it If you don't have the C++ toolchain installed this is missing, but then you can't' debug C++ anyway --> <LibToolPath Condition="Exists('$(DevEnvDir)\..\..\VC\bin')">$(DevEnvDir)\..\..\VC\bin</LibToolPath> </PropertyGroup> <DllExportTask Platform="$(Platform)" PlatformTarget="$(PlatformTarget)" CpuType="$(CpuType)" EmitDebugSymbols="$(DebugSymbols)" DllExportAttributeAssemblyName="$(DllExportAttributeAssemblyName)" DllExportAttributeFullName="$(DllExportAttributeFullName)" Timeout="$(DllExportTimeout)" KeyContainer="$(KeyContainerName)$(AssemblyKeyContainerName)" KeyFile="$(KeyOriginatorFile)" ProjectDirectory="$(MSBuildProjectDirectory)" InputFileName="$(TargetPath)" FrameworkPath="$(TargetedFrameworkDir);$(TargetFrameworkDirectory)" LibToolPath="$(LibToolPath)" LibToolDllPath="$(DevEnvDir)" SdkPath="$(SDK40ToolsPath)"/> <!-- $(MSBuildProgramFiles32) points to the 32 bit program files dir. On 32 bit windows usually C:\Program Files\ On 64 bit windows usually C:\Program Files (x86)\ $(ProgramW6432) points to the 64bit Program Files (on 32 bit windows it is blank) --> <!-- Uncomment the following block to copy the dll to your NPP plugin folder. --> <!-- Steps below will identify notepad++ location. It will create a "Demo" --> <!-- directory in the plugin folder and then copy the dll to it. --> <!-- <MakeDir Directories="$(MSBuildProgramFiles32)\Notepad++\plugins\$(TargetName)\" Condition="Exists('$(MSBuildProgramFiles32)\Notepad++\plugins\') AND !Exists('$(MSBuildProgramFiles32)\Notepad++\plugins\$(TargetName)\') AND '$(Platform)'=='x86'" /> <Copy SourceFiles="$(TargetPath)" DestinationFolder="$(MSBuildProgramFiles32)\Notepad++\plugins\$(TargetName)\" Condition="Exists('$(MSBuildProgramFiles32)\Notepad++\plugins\$(TargetName)\') AND '$(Platform)'=='x86'" ContinueOnError="false" /> <MakeDir Directories="$(ProgramW6432)\Notepad++\plugins\$(TargetName)\" Condition="Exists('$(ProgramW6432)\Notepad++\plugins\') AND !Exists('$(ProgramW6432)\Notepad++\plugins\$(TargetName)\') AND '$(Platform)'=='x64'" /> <Copy SourceFiles="$(TargetPath)" DestinationFolder="$(ProgramW6432)\Notepad++\plugins\$(TargetName)\" Condition="Exists('$(ProgramW6432)\Notepad++\plugins\$(TargetName)\') AND '$(Platform)'=='x64'" ContinueOnError="false" /> --> </Target> </Project>