Not able to display 404 error in prod environment - symfony

Question

When I try to throw a simple throw $this->NotFoundHttpException('We do not currently have a website configured at this address. Please visit our website for more information or contact our support team');in dev environment, it works fine. But when I do the same in prod environment I get 500 server error.
Any ideas?
Here are screenshots of my dev and prod log files
Note: 500 error only happens when I use www in the url in prod env. On using any other word eg. nike, this is what i get
Here is the dev env result for the normal www.blore.eduflats.com url

Answer 1

According to the symfony documentation in order to return a 404 from your controller you need to do the following:
throw $this->createNotFoundException('The product does not exist');
Whereas, you have
throw $this->NotFoundHttpException
The error you are seeing is telling you that NotFoundHttpException does not exist. To fix your problem simply replace NotFoundHttpException with createNotFoundException

Answer 2

You call Eduflas.. UniversityResolver->NotFoundHttpException();
If you want to trhow exception like this, you should declare it.
Symfony Controller have $this->createNotFoundException('Something Not found');
You can throw 404 like this:
use Symfony\Component\HttpKernel\Exception\NotFoundHttpException
//...
throw new NotFoundHttpException("Not found");
Use this way to be sure that Exception exist and test it.
Anyway clear your production and dev cache to be sure you use "the same code".
Last thing that come to my head - its possible you override error pages and you make something to your error.html.twig or error404.html.twig and you got different pages.
EDIT
When i enter your http://blore.eduflats.com/ i got
"array(29) { ["HTTP_HOST"]=> string(18) "blore.eduflats.com" ["HTTP_USER_AGENT"]=> s..."
Anyway your dev env. got error too so how it can work on prod env...
If you throw NotFoundException in dev you should get symfony debugger page and this error. In porduction this error is catch with ExceptionController and display blank error page (user should not see exceptions, only 500 error)