Issues of a specific tracker do not appear on the Roadmap page in Redmine
The Roadmap page displays the versions created in the Redmine project and the list of issues associated with each version. However, it does not display all issues. It displays only the issues of trackers for which the "Issues displayed in roadmap" checkbox is turned on in the tracker edit page.
For example, among the trackers registered in Redmine by default, "Support" has "Issues displayed in roadmap" turned off. For this reason, issues of the "Support" tracker do not appear on the Roadmap page.
Why "Support" does not appear in the roadmap by default
The Roadmap page manages the list of features and bug fixes that are planned for a specific version of the software. Issues of the "Support" tracker are not directly related to the features of the released software (they do not involve changes to the source code). This is probably the reason why Redmine does not display them by default.
