Check the file size of the Sierra installer, sometimes App Store only download the fast installer about couple of MB in size, and not the full installer ~5-6GB.
You need to have the full installer to create the bootable USB.
Unfortunately there’s no way to control what type of installer that gets downloaded from App Store even same link from Apple may yield different results on different computer.
I downloaded the sierra dmg from App store. When i use install disk creator to create a bootable usb. It said it lacking installESD.dmg. may i know what is the solution?