If you program using Vulkan on Windows and you see that Vulkan layers stopped working (especially after updating graphics driver or Vulkan SDK), first thing to try is to uninstall Vulkan SDK and install it again. Also restart your computer, to be sure that environmental variables are updated. But sometimes it doesn't help or it even makes things worse.
If you are still not able to successfully find and enable
VK_LAYER_LUNARG_standard_validation in your code, or you try to enable
VK_LAYER_LUNARG_api_dump using environmental variable but can't see it working, or have problem with any other layer, first thing you can try is to issue
vulkaninfo console command. If you see some errors about "JSON", it clearly indicates that there is a problem with configuration of Vulkan in your system, regarding paths to layer DLLs and their JSON descriptions.
Either way, the thing I recommend is to launch
regedit (Registry Editor) and check values in following keys:
They should contain paths to valid JSON files that describe installed Vulkan layer DLLs. "ExplicitLayers" is the list of layers that can be manually enabled either programatically via
VkInstanceCreateInfo::ppEnabledLayerNames, or via environmental variable
VK_INSTANCE_LAYERS. "ImplicitLayers" is the list of layers loaded automatically by each Vulkan app (e.g. one added by Steam or RenderDoc). For further details see article: "Vulkan Validation and Debugging Layers".
It looks that the installer of Vulkan SDK can mess up these registry entries. Yesterday, after uninstalling old SDK and installing new one, I found there entries from both versions. Today, my colleague found these registry keys completely empty. So whenever you have problems with Vulkan layers on Windows, take a look at the registry.
Update 2018-08-27: There is Issue #38 on GitHub - Vulkan-Ecosystem about this.