This mean that the WonderPush SDK script is not included in your web page.
If there is a syntax error earlier in the script, its execution is aborted and it might hence be possible that you do not reach the place where the WonderPush SDK is included.
If you used Google Tag Manager or similar tools to inject it, note that adblockers might prevent those tools to run in your pages.
Or you might simply have removed the script by mistake.
Looking at your website, I cannot see the place where the SDK is included.
If I look at your Italian website, I see it served from your “
Please check that you did not remove the script integration.