Vercel serverless Node.js API (NOT Next.js) can't auth user with Supabase

error:  AuthApiError: Internal server error
    at C:\XXX\node_modules\@supabase\gotrue-js\src\lib\fetch.ts:41:16
    at processTicksAndRejections (node:internal/process/task_queues:95:5) {
  __isAuthError: true,
  status: 500
}

{"component":"api","error":"invalid claim: subject missing","level":"error","method":"GET","msg":"Unhandled server error: invalid claim: subject missing","path":"/user","referer":"","remote_addr":"xxx.xxx.xxx.xxx","time":"2022-10-29T19:23:01Z","timestamp":"2022-10-29T19:23:01Z"}

const supabaseClient = createClient(supabaseUrl, supabaseKey);

const user = await supabaseClient.auth.getUser();