Hello Arsen,
as indicated here Docs
Due to browser security policies, all files must be installed behind a webserver of any kind (Apache, IIS, nginx, etc.) for publishing to work. It will not work locally on your computer from a file:// URL.
You will have to export the project to Epub3 to be able to use it offline in a reader (e.g. iBooks or Thorium Reader).
Best,
Ric
The PubCoder Team