SDK JAVA 0.3.4 Stop working?

I am presenting an error with the integration of MercadoPago's JAVA 0.3.4 SDK. It has been in operation for 4 years and began to present problems in the month of May to date.

The error occurs when creating a preference, it is with the basic ckeckout.

Obtains accessToken without problem, but upon receiving the response it gives an error:

This is the method of the SDK that gives error:

public JSONObject createPreference(JSONObject preference) throws JSONException, Exception {
        String accessToken;
        try {
            accessToken = this.getAccessToken();
        } catch (Exception var5) {
            JSONObject result = new JSONObject(var5.getMessage());
            return result;
        }
        JSONObject preferenceResult = MP.RestClient.post("/checkout/preferences?access_token=" + accessToken, preference);
        return preferenceResult;
    }

The preferenceResult returns this: {"status":500,"response":{"message":"Oops! Something went wrong...","error":"internal_error","status":500,"cause":[]}}

What could it be? Is that SDK still working?