As soon as I posted this I remembered that I needed to add the new user to my accesscontrollist file. In hassio that is located at /share/mosquitto/accesscontrollist. I added the following

user blueiris
topic readwrite #

Were you able to sort this out. I'm using an MQTT broker provided through HomeAssistant (Hass.io). I to have other things running through the broker, so I think its working fine. Curious.