Follow these steps to inspect your website and check the tracking script.
In Google Chrome:
Go to your website
Right click and choose "inspect"
Click on the Network tab
Filter on iztag.js
Refresh your page
The tag will appear if everything is correctly installed.
If you don't get any request back, please double-check the script installation once again.
This is how it should look when the script is beeing installed on your website.