Upgrade from 12.10.14 to 13.0.0 fails - 502

Hi,
yesterday I made the upgrade as in the title, but I can’t login. I get a 502 error " Whoops, GitLab is taking too much time to respond."
I have CentOS 6
sudo yum install gitlab-ce-13.0.0-ce.0.el6.x86_64
sudo yum install gitlab-ce-13.0.14-ce.0.el6.x86_64

after installation and reboot, i can’t see unicorn
sudo gitlab-ctl restart
ok: run: alertmanager: (pid 2363) 0s
ok: run: gitaly: (pid 2403) 0s
ok: run: gitlab-exporter: (pid 2444) 1s
ok: run: gitlab-workhorse: (pid 2480) 0s
ok: run: grafana: (pid 2504) 1s
ok: run: logrotate: (pid 2530) 0s
ok: run: nginx: (pid 2536) 0s
ok: run: node-exporter: (pid 2581) 1s
ok: run: postgres-exporter: (pid 2587) 0s
ok: run: postgresql: (pid 2633) 0s
ok: run: prometheus: (pid 2635) 0s
ok: run: puma: (pid 2725) 0s
ok: run: redis: (pid 2771) 0s
ok: run: redis-exporter: (pid 2888) 0s
ok: run: sidekiq: (pid 2902) 0s

I am asking for help and tips to solve the problem

Unicorn was replaced with puma it is why you dont see it.

Suggest doing:

gitlab-ctl reconfigure

And if after doing:

gitlab-ctl restart

still doesnt work, reboot the server. If still having problems check all the logs for errors.

Right, the puma replaced the unicorn, but it didn’t have the correct configuration.
I added the appropriate parameters (ports) for the puma and reconfigured the gitlab.
The system works again;)

Thanks for the update and sharing the solution, @Jachym . Glad you got it working!