Hi,
The dproj does not contain proper namespaces for Win64x, we are currently looking into this issue. You can fix this manually by going to packages\d12\TMSVCLIWPkg.dproj edit via notepad and change the base_win64x property group by adding the namespace
<PropertyGroup Condition="'$(Base_Win64x)'!=''">
*<DCC_Namespace>Winapi;System.Win;System;Data.Win;Datasnap.Win;Web.Win;Soap.Win;Xml.Win;$(DCC_Namespace)</DCC_Namespace>*
<BT_BuildType>Debug</BT_BuildType>
<VerInfo_IncludeVerInfo>true</VerInfo_IncludeVerInfo>
<VerInfo_Keys>CompanyName=;FileDescription=$(MSBuildProjectName);FileVersion=1.0.0.0;InternalName=;LegalCopyright=;LegalTrademarks=;OriginalFilename=;ProgramID=com.embarcadero.$(MSBuildProjectName);ProductName=$(MSBuildProjectName);ProductVersion=1.0.0.0;Comments=</VerInfo_Keys>
<VerInfo_Locale>1033</VerInfo_Locale>
</PropertyGroup>
Then run tms.exe build again