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Question

The job is stuck because your runners have tags but your jobs don't. Follow these 4 steps to enable your runner to run without tags:

Or set tags to your jobs. For more info: Configuration of your jobs with .gitlab-ci.yml - Tags

Make sure you are using the correct tag i.e. whatever present corresponding to the configured runner for your project.

In your case it would be like :

maven-build:
 image: maven:3-jdk-8
 stage: build
 tags: my project ci-cd
 script: "mvn package -B"
 artifacts:
 paths:
  - target/*.jar

It was quite simple on my side, I just run gitlab-runner run on my computer

Also you can tag your jobs using the following syntax in file .gitlab-ci.yml:

stages:
  - check
  - build
  - test
  - analyze
  - package
  - release
  - deploy
nohttp:
  stage: check
  tags:
    - dev

Besides not to forget to add tag "dev" to your project's specefic/shared runner.