Why is iFrame OneSignal not loading on Laravel?

Question

Laravel

There is a site on Laravel, the OneSignal push notification service is attached to it.
As I understand it, in production Laravel does not allow loading code from an iframe, because I get Onesignal script error:

OneSignal: Could not load iFrame with URL https://*****.onesignal.com/webPushIframe. Please check that your 'subdomainName' matches that on your OneSignal Chrome platform settings. Also please check that your Site URL on your Chrome platform settings is a valid reachable URL pointing to your site.

I checked the subdomain and the key - everything is correct. How to make OneSignal work?)