Connection Issues with Simulator

I have the simulator up and running via ./ run simulator --local, however I cannot figure out why I cannot run my sandbox code. I have a class SandBox(MQTTModule), however when I try to do box = Sandbox() followed by box.run_non_blocking(), I get the following error:

I am also not sure how to connect via MQTTExplorer. I have the host as and the port as 5760, but it says “Not supported auth packet for this version MQTT”. For context, I wanted to test autonomous flight paths on the simulator using QGroundControl before testing on our real drone.