maktouch: Runner can't connect to GitLab because version 9.0 of Runner requires GitLab 9.0. We've noticed this in the release blog post: https://about.gitlab.com/2017/03/22/gitlab-9-0-released/#git... :)
The reason is that in 9.0 we've prepared a new API for Runner requests (as part of new v4 version of API) and Runner 9.0 is using only this version.
Version v1 of the CI API is still supported by Runner 1.10.X and 1.11.X. On GitLab's side it will be supported until August 2017 and until then we will also support Runner 1.11.X.
I run my fleet of runners in pre-emptible instances on GCP (they die after 24h).
I forgot to pin the version in my startup script, so all it did was a simple apt-get install gitlab-ci-multi-runner.
For some reason, version 9 of the gitlab runner cannot connect to our Gitlab (it fires a 404 on register).
Anyways, look like 9 is a cool release, but we won't be upgrading until the sidebar comes back (did a little poll in the team and it 100% was in favour of the sidebar)