Queries break when in production on Vercel; work on localhost

The query is called like this:

  const { data } = api.useQuery(["user.!getCount"], {
    refetchInterval: interval * 1000,
    onSuccess: () => ...
  }

  const { data } = api.useQuery(["user.!getCount"], {
    refetchInterval: interval * 1000,
    onSuccess: () => ...
  }

  const { data } = api.useQuery(["user.!getCount"], {
    refetchInterval: interval * 1000,
    onSuccess: () => ...
  }

  const { data } = api.useQuery(["user.!getCount"], {
    refetchInterval: interval * 1000,
    onSuccess: () => ...
  }

every query works on localhost, but once it's deployed to Vercel they all give this same error