after migration Fatal error: Class 'Symfony\Component\HttpKernel\Kernel' not found in

[tosal]

hi there, finally i finished my new site. Everything works good in test site but when i moved it to the final link i've got this error
Fatal error: Class 'Symfony\Component\HttpKernel\Kernel' not found in ...../app/AppKernel.php on line 34

and nothing works.

What does it mean how can i fix it?

Edited April 15, 2019 by tosal
lost partial text (see edit history)

[tosal]

i forgot to say that ps version is 1.7.5.1