Hello becki85,
Thanks for using Apple Support Communities, it's great to have you here.
To enable cookies on your iPhone 11, you'd want to follow the guidance in this article to unblock cookies: Clear the history, cache, and cookies from Safari on your iPhone, iPad, or iPod touch - Apple Support. This article has a ton of great information but we'll copy and paste the most pertinent info below to make it easier:
Block cookies
A cookie is a piece of data that a site puts on your device so that site can remember you when you visit again.
To block cookies:
1. Go to Settings > Safari > Advanced.
2. Turn on Block All Cookies.
As you can tell, those steps are for blocking cookies but if you use that information to unblock cookies instead, you should be good to go.
We hope this information is helpful!
Have a great day.