Admin shows upgrade required, but already at latest

Site shows:

However, running the update shows:
root@fsgit:~# sudo apt-get update && sudo apt-get install gitlab-ce

gitlab-ce is already the newest version (11.1.0-ce.0).

root@fsgit:~# lsb_release -a

No LSB modules are available.

Distributor ID: Ubuntu

Description: Ubuntu 16.04.6 LTS

Release: 16.04

Codename: xenial

It seems like you don’t have an apt source configured that carries the newer versions of GitLab. Look at the installation guide, download the script mentioned there and read it to figure out what to add to your sources.list.

Addition: Newest version is 12.4.2, so you’re far from the newest version.