After a while browser started to show error like "Website is down or has been moved". Had to remove Protocols h2 http/1.1 to make website work again. 0 errors(just some notices and warnings) in apache error_log :/
//Also tried to stop nginx
Found something in /var/www/vhosts/<domain_name>/logs/proxy_error_log but don't think this is the problem.
Let's check a few things;
[root@plesk ~]# httpd -v
(should come back 2.4.29)
[root@plesk ~]# apachectl -t -D DUMP_MODULES | grep http2
(show come back with 2 results, http2_module and proxy_http2_module)