I checked your repository and the releases you have created, and I found few questions:
1) The workflow YAML file " mvndeploy.yml" is only located on the develop branch.
2) All the releases you have created are from the master branch.
Here are few points need you pay attention to:
1) After you have created a new workflow, this workflow will not be listed on " Actions" tab until it is triggered for the first time.
2) The GITHUB_REF of the release event is a tag ref, and Github will only reference the workflow YAML files on this tag ref, and the tag ref is created from the specified branch (master in your cases).
3) You can’t use the event occurs on a branch/tag ref to trigger the workflows located on another branch/tag ref.
So, my suggestions:
1) If you want to trigger the release workflow on the develop branch, when you create a new release, you should select the tag created from the develop branch.
2) Similarly, if you create release from the master branch, and want to trigger the release workflow, you should make sure the YAML file also has been existing on the master branch, and select the tag created from the master branch when creating a new release.
More details about Release event, you can reference here: https://help.github.com/en/actions/reference/events-that-trigger-workflows#release-event-release