Dashboard not working, TypeError: OFF is not JSON serializable

I haven’t seen this specific error before but I see you are running AppDaemon 2.1.12 with python 3.5.3 - this can cause other problems. I suggest you upgrade to AppDaemon 3,0 as an initial step and see if the problem persists - if it does we can track it down in the 3,0 branch as a lot has changed.