I am using the datacenter edition of JIRA (8.20.2) and its API and I have a customfield, customfield_10500 that can have one of multiple string values.
My problem is that I need to get the text value of the customfield, but I seem unable to get this information.
I have this data for a specific issue and the "customfield" returns an ID:

So I need the value of customfield ID 10620 - in my case it is the team name, e.g. "My Team 1".
It is my understanding that it should be possible to query the customfields by this direct API call:

.. but if I do this, then I get this 404 error:

Can anyone help me solving this problem? :-) I would really hate hardcoding these IDs in my code.