Not able to add sub issue using gh api

[mounakrishna99]

REST API adding sub issue problem

I generated a Fine grain PAT with writable access to Issues for the repository permissions along with other requirements of writable Github Projects etc. I am able to create issues using that PAT token. But when I try to add a sub-issue as mentioned in the API document https://docs.github.com/en/rest/issues/sub-issues?apiVersion=2022-11-28#add-sub-issue, I get status error as 403 stating resource not accessible.

I tried a new temporary Fine grain PAT token with access to all and ran, but still the same issue.

I even tried with a classic PAT token. In this case, I got status: 404 with message as "Not Found".

Am I missing something in giving the permissions or is this a bug?