Why "com.pyxis.greenhopper.jira" information is missing for some scrum projects?

Question

I have an application which is accessing the JIRA cloud using Jira Software Cloud REST API. According to mentioned REST API documentation, information about sprint or epic is under custom fields which is identified by "com.pyxis.greenhopper.jira:gh-sprint" (in case of sprint field). The problem is that for 2 projects this information is not returned. I have no idea why. I looked at project settings, Jira settings and Administration, but no results. Both failing projects are software, scrum and use the "Classic software" type (like others). What might be the problem? Exact call which my app is requesting is: https://.atlassian.net/rest/api/2/issue//editmeta I tried also with version 3 of API, but with the same results. I got information, that those projects might be imported from older JIRA server version.

Dariusz Wilczak · Accepted Answer

Thanks for reply @Andy Heinzer , but it wasn't a problem with authentication - it was working for all projects except two (all in the same JIRA Cloud).

Solution in my case was to added the "Sprint" field in the project screen. Those 2 projects used the same screen, were "Sprint" field was removed. Why? I don't know, but now it works :)