This page makes use of the GitHub API to store your charts (a GitHub account is required since March 19, 2018). There’s a rate limit of 60 anonymous API requests per-hour per-visitor. To avoid reaching this limit, this sofware tries to use the caching mechanisms available in modern browsers. If you cannot retrieve a chart, please try later.
To build your chart (particularly, to fill in the time, data, by or grouped fields), you might need to read the documentation or check some sample code. See some visualizations done with Visual Maker.