graphQL api unavailable

I am a developer on a project that wants to pull data from GitLab and show it in a UI that makes sense for our project via a React app. To that end, I am experimenting with graphQL. I am a bit stuck right off the bat though because I am unable to connect to our server via the api/graphql endpoint using curl or graphQL playground. (Note: we are using a self-managed instance.) I can use graphiQL explorer, but connecting to the box via curl (or graphQL playground) returns an internal server error. I saw in the docs that if you’re running GitLab 11 or 12 you may need to turn on the graphql feature. Not sure what version we’re running, but I did that, and still cannot connect. I get a return code of 500. What more can I do?