CI Job stuck because of tag, but runner with tag is available

Summary

My CI job is not executed because of a missing tag:

But on the runners page, I have a runner with that tag:

How can I further debug this?

Steps to reproduce

Add Tags to your CI jobs.

Output of checks

Results of GitLab environment info

Expand for output related to GitLab environment info

System information
System:		Ubuntu 18.04
Current User:	git
Using RVM:	no
Ruby Version:	2.4.4p296
Gem Version:	2.7.6
Bundler Version:1.16.2
Rake Version:	12.3.1
Redis Version:	3.2.11
Git Version:	2.17.1
Sidekiq Version:5.1.3
Go Version:	unknown
GitLab information
Version:	11.1.2
Revision:	35936b0b628
Directory:	/opt/gitlab/embedded/service/gitlab-rails
DB Adapter:	postgresql
URL:		https://xxx
HTTP Clone URL:	https://xxx/some-group/some-project.git
SSH Clone URL:	ssh://xxx/some-group/some-project.git
Using LDAP:	yes
Using Omniauth:	no
GitLab Shell
Version:	7.1.4
Repository storage paths:

• default: /var/opt/gitlab/git-data/repositories Hooks: /opt/gitlab/embedded/service/gitlab-shell/hooks Git: /opt/gitlab/embedded/bin/git

Results of GitLab application Check

Expand for output related to the GitLab application check

Checking GitLab Shell ...
GitLab Shell version >= 7.1.4 ? ... OK (7.1.4)
Repo base directory exists?
default... yes
Repo storage directories are symlinks?
default... no
Repo paths owned by git:root, or git:git?
default... yes
Repo paths access is drwxrws---?
default... yes
hooks directories in repos are links: ...
6/2 ... ok
5/3 ... ok
6/4 ... ok
5/5 ... ok
6/6 ... ok
6/7 ... ok
7/8 ... ok
7/9 ... ok
6/10 ... ok
7/11 ... ok
6/12 ... ok
7/13 ... ok
7/14 ... ok
7/15 ... ok
7/16 ... ok
8/17 ... ok
6/18 ... ok
41/19 ... ok
41/20 ... ok
6/21 ... ok
6/22 ... ok
41/24 ... ok
17/25 ... ok
6/26 ... ok
5/27 ... ok
6/28 ... ok
6/29 ... ok
6/30 ... ok
6/31 ... ok
41/32 ... ok
43/33 ... ok
5/34 ... ok
6/35 ... ok
41/36 ... ok
22/37 ... ok
24/39 ... ok
24/40 ... ok
8/41 ... ok
43/42 ... ok
22/43 ... ok
43/44 ... ok
39/45 ... repository is empty
30/47 ... ok
22/48 ... ok
22/49 ... ok
33/51 ... ok
22/52 ... ok
39/53 ... repository is empty
43/54 ... repository is empty
39/55 ... repository is empty
39/56 ... repository is empty
39/57 ... repository is empty
39/58 ... repository is empty
39/59 ... repository is empty
39/60 ... repository is empty
55/61 ... ok
56/62 ... ok
56/63 ... ok
56/64 ... ok
55/65 ... ok
56/66 ... ok
39/67 ... repository is empty
5/68 ... repository is empty
60/69 ... ok
60/70 ... ok
60/71 ... repository is empty
67/72 ... ok
67/73 ... ok
67/74 ... repository is empty
24/75 ... repository is empty
Running /opt/gitlab/embedded/service/gitlab-shell/bin/check
Check GitLab API access: OK
Redis available via internal API: OK
Access to /var/opt/gitlab/.ssh/authorized_keys: OK
gitlab-shell self-check successful
Checking GitLab Shell ... Finished
Checking Sidekiq ...
Running? ... yes
Number of Sidekiq processes ... 1
Checking Sidekiq ... Finished
Checking Reply by email ...
IMAP server credentials are correct? ... yes
Init.d configured correctly? ... skipped
MailRoom running? ... skipped
Checking Reply by email ... Finished
Checking LDAP ...
Server: ldapmain
LDAP authentication... Success
LDAP users with access to your GitLab server (only showing the first 100 results)
xxx
Checking LDAP ... Finished
Checking GitLab ...
Git configured correctly? ... yes
Database config exists? ... yes
All migrations up? ... yes
Database contains orphaned GroupMembers? ... no
GitLab config exists? ... yes
GitLab config up to date? ... yes
Log directory writable? ... yes
Tmp directory writable? ... yes
Uploads directory exists? ... yes
Uploads directory has correct permissions? ... yes
Uploads directory tmp has correct permissions? ... yes
Init script exists? ... skipped (omnibus-gitlab has no init script)
Init script up-to-date? ... skipped (omnibus-gitlab has no init script)
Projects have namespace: ...
6/2 ... yes
5/3 ... yes
6/4 ... yes
5/5 ... yes
6/6 ... yes
6/7 ... yes
7/8 ... yes
7/9 ... yes
6/10 ... yes
7/11 ... yes
6/12 ... yes
7/13 ... yes
7/14 ... yes
7/15 ... yes
7/16 ... yes
8/17 ... yes
6/18 ... yes
41/19 ... yes
41/20 ... yes
6/21 ... yes
6/22 ... yes
41/24 ... yes
17/25 ... yes
6/26 ... yes
5/27 ... yes
6/28 ... yes
6/29 ... yes
6/30 ... yes
6/31 ... yes
41/32 ... yes
43/33 ... yes
5/34 ... yes
6/35 ... yes
41/36 ... yes
22/37 ... yes
24/39 ... yes
24/40 ... yes
8/41 ... yes
43/42 ... yes
22/43 ... yes
43/44 ... yes
39/45 ... yes
30/47 ... yes
22/48 ... yes
22/49 ... yes
33/51 ... yes
22/52 ... yes
39/53 ... yes
43/54 ... yes
39/55 ... yes
39/56 ... yes
39/57 ... yes
39/58 ... yes
39/59 ... yes
39/60 ... yes
55/61 ... yes
56/62 ... yes
56/63 ... yes
56/64 ... yes
55/65 ... yes
56/66 ... yes
39/67 ... yes
5/68 ... yes
60/69 ... yes
60/70 ... yes
60/71 ... yes
67/72 ... yes
67/73 ... yes
67/74 ... yes
24/75 ... yes
Redis version >= 2.8.0? ... yes
Ruby version >= 2.3.5 ? ... yes (2.4.4)
Git version >= 2.9.5 ? ... yes (2.17.1)
Git user has default SSH configuration? ... yes
Active users: ... 29
Checking GitLab ... Finished