WebDev Module: 404 Not Found when accessing HTML via Mounted Folder

Your mounted folder path appears to not be physically in the gateway machine, but in a network share. In Windows, by default, the account running the background service cannot access network shares.

There are numerous discussions on this forum about using UNC paths combined with a custom background user account, like this one:

But it is more robutst to simply place the files directly in the gateway filesystem.