Remember that, when printing from the browser, you must use https, localhost o 127.0.0.1. It won't work on sites without HTTPS nor localhost with a different port than 80 (which is the default ) nor IP. If you want to print on the local area network, check:How to print on a network printer
If the examples are not working, make sure that:

1. The plugin is running in the background. Download it from: https://github.com/parzibyte/plugin-impresora-termica-v3/releases/latest/
2. Your printer is shared and has a friendly name as indicated in: https://parzibyte.me/blog/en/2019/10/13/how-to-share-printer-windows/

When printing, the cash drawer should be opened