Are you submitting that request as the add-on user, or are you submitting it on behalf of an actual end-user? I’m wondering if somehow the field isn’t visible to the calling user.
I noticed that I tried to apply the api to general ‘Select List’ field created by hand on ‘Custom fields’ Management Screen.
The rest api document says,
Select list issue fields can be defined by a Connect add-on. The add-on that provided the field can add,
remove and update the options using the methods defined in this resource.
@abe.kenichi - so what did you end up doing here? I am in a similar situation and I successfully created a custom select field through the API but I am still not able to get a list of options by any of the fieldKeys I’ve tried.