No project could be found with id XXXXX
Symptoms
When trying to access Roles, Versions and Components inside a project under the Project Administration, the content is not displayed and the page appears to keep loading. When using a browser's developer tools to investigate, a 404 error appears:
Diagnosis
The project's key contains only number characters. Since JIRA 6.1, it is not possible to customize the project key pattern allowing only numbers, but it is still possible to see this in newer releases when JIRA was upgraded from a version in which this was allowed.
Cause
This problem happens because JIRA currently allows both the Project Key or Project ID in the REST API call (/rest/api/2/project/{projectIdOrKey}/versions). As the Project Key only contains numbers, the REST API assumes it as the Project ID, and consequently cannot find a project with that ID, which causes the 404 error to happen.