Jira Issue REST API is missing issuelinks data

One of our client is having Jira DC v9.4.6. We use Jira REST API v2 to fetch the Jira issue details with issue links to render our App content. But on a particular client’s Jira DC instance, Jira REST API is not returning the issuelinks in the API response.

Points to consider:

  1. We are using the following Jira REST API
  2. On other client’s instances, the same code is working fine without any issues.
  3. The Jira’s remote link API is returning an empty list.
  4. We also tried to add the Linked Issues field on all the screens for each issue type but nothing worked.
  5. We are able to see the issue links on the Jira issue page, but not via the REST API.
  6. This REST API missing issue links problem is there on some of the issues, not on all issues.

I am just waiting for some expert guidance on resolving this issue.