Beginning with the July 2017 update, Microsoft is now pushing out a 64-bit version of Visual Studio Code. If you have an existing 32-bit version installed, you will not automatically be updated to the 64-bit version.
All you need to do though is manually uninstall your 32-bit version and install the 64-bit one. All of your existing extensions will be picked up by the new version and should continue to work.
Grab the 64-bit version here.