This zip is missing the Libs folder contents.

Your ItemWatch.toc requires these four files/folders (unchanged from your
existing working install - these are standard, widely-used libraries):

  Libs\LibStub\LibStub.lua
  Libs\CallbackHandler-1.0\CallbackHandler-1.0.lua
  Libs\LibDataBroker-1.1\LibDataBroker-1.1.lua
  Libs\LibDBIcon-1.0\LibDBIcon-1.0.lua

Before uploading: copy these four folders in from your current, working
ItemWatch install (or your AddOns folder) so they sit alongside
ItemWatch.lua and ItemWatch.toc inside this ItemWatch/ folder, then
delete this text file and re-zip.

(Why this note exists: the project file that should have been
LibDataBroker-1.1.lua actually contained CallbackHandler-1.0's code
instead - looks like a mislabeled upload somewhere along the way. Rather
than guess at replacing it from memory, it's safer for you to pull the
real files from your known-working copy.)
